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Leaving Certificate

Chemistry

Practical Workbook

Name __________

© Peter J Jackson BSc.; HDE; MIBI

Lab Safety Agreement

3333333

© Peter J Jackson 2012

Science SafetyDO NOT ENTER the Laboratory without permission.

NOTHING must be TASTED, EATEN or DRUNK in the Laboratory.

USE EQUIPMENT ONLY when permitted to do so by the Teacher. Make sure you know exactly what you are supposed to do. If in doubt, ask the Teacher.

Always CHECK the LABEL on the BOTTLE is exactly the same as the material you require. If in doubt, ask the Teacher.

LONG HAIR must always be tied back securely.

Always wear SAFETY SPECTACLES when instructed to do so.

Any CUTS, BURNS or other ACCIDENTS must be reported at once to the Teacher.

CHEMICAL SPILLS on skin or clothing must be washed at once with plenty of water and reported to the Teacher.

Any substance accidentally taken into the mouth must be spat out immediately and the mouth washed out with plenty of water. The matter is to be reported to the Teacher immediately.

Always WASH YOUR HANDS after practical work.

NO RUNNING AROUND or rough behaviour in the laboratory.

Do NOT throw things or squirt liquids in the laboratory.

Gowns must NOT be worn in the lab.

Signature _______________________________________

3

Mandatory Experiments Form V 2012 done

1. Flame Tests [Li, Na, K, Ba, Sr, Cu] 5

2. Redox Reactions of Halogens and the Halogens as Oxidising Agents 7

3. Displacement Reactions of Metals - [Zn with Cu2+ and Mg with Cu2+] 11

4. Tests for Anions in Aqueous Solutions 13

5. Determination of the Relative Molecular Mass of a Volatile Liquid 14

6. Preparation of a Standard Solution of Sodium Carbonate 18

7. Standardisation of a Hydrochloric Acid Solution using a Standard Sodium Carbonate. solution 20

8. Hydrochloric acid / Sodium hydroxide titration and use of this reaction to make the salt NaCl 23

9. Determination of the Concentration of Ethanoic Acid in Vinegar 25

10. Determination Percentage Water of Crystallisation in a Sample of Hydrated Sodium Carbonate 28

11. A Potassium Manganate (VII) / Ammonium Iron(II) Sulphate Titration 31

12. Determination of the Amount of Iron in an Iron Tablet 33

13. An Iodine \ Thiosulphate Titration 36

14. Determination of the Percentage of Hypochlorite in Bleach [Parazone diluted the night before] 40

15. Determination of the Heat of Reaction of Hydrochloric Acid with Sodium Hydroxide 44

16. Preparation and Properties of Ethyne 46

17. Monitoring the rate of production of oxygen from hydrogen peroxide using MnO2 catalyst. 48

18. Effect of Concentration on Reaction Rate using Sodium Thiosulphate and Hydrochloric Acid. 51

19. Effect of Temperature on Reaction Rate using Sodium Thiosulphate and Hydrochloric Acid. 54

20. Recrystallisation of Benzoic Acid and Determination of its Melting Point 57

21. Preparation of Soap 60

22. Preparation and properties of Ethene 62

23. Preparation and Properties of Ethanal 64

24. Preparation and Properties of Ethanoic Acid 67

25. Extraction of Clove Oil from Cloves [or similar] by Steam Distillation 70

26. Separation of a Mixture of Indicators using Paper Chromatography 72

27. Experiments to Illustrate Le Chatelier’s Principle to show Effects of Temperature Changes 73

28. Experiments to Illustrate Le Chatelier’s Principle to show Effects of Concentration Changes 75

29. Colorimetric Experiment to estimate Free Chlorine in Bleach 77

30. Determine Total Suspended and Dissolved Solids in p.p.m. by Filtration and Evaporation. 80

31. Determination of pH 83

32. Estimation of Total Hardness using EDTA [balanced equation required] 84

33. Estimation of Dissolved Oxygen Content of a Water Sample by Redox Titration 87


Experiment 1 Date ____________

Flame Tests

Materials and Apparatus

o Nichrome wire loopo Clock glasso Bunsen burnero Sodium chlorideo Calcium chlorideo Copper chlorideo Lithium chlorideo Potassium chlorideo Strontium chlorideo Concentrated Hydrochloric Acid

Method

o Light the bunsen burner and open the air hole fully to get a non-luminous [blue] flame

o Moisten a sample of each type of crystals using conc. HClo Pick up a sample using clean nichrome wireo Place the sample in the flame [near the edge of the light blue cone is best]o Observe the colour of the flameo In the case of potassium look at the flame through blue glass as wello In the space below draw a diagram of a sample being testedo Record you observations in the table on the next page


Results

Metal Flame colour Other notes

Sodium

Potassium

Lithium

Copper

Strontium

Barium

Conclusion

Each metal ___________________________________________________________

______________________________________________________________________

_______________________________________________________________________

Additional Activities

Look at the light from a sodium vapour lamp through a spectroscope

Draw what you see when you look through the spectroscope

What is this called?

_______________________________________________________

What is it evidence of?

_____________________________________________________



Redox Reactions of Group VII Elements

Safety Precautions

o KMnO4 – powerful oxidising agent and irritanto HCl - corrosiveo Cl2 - poisonouso KI – irritanto Wear safety glasses and rubber gloves

Experiment 2a Reaction of Cl2(g) with KI(aq)

Apparatus

o Test tubeso Potassium manganate(VII) crystalso Conc. Hydrochloric acido Potassium iodide solution o Litmus paper [blue]

Procedure

o Pour some potassium iodide [KI] solution into a test tube.

o Place some potassium manganate(VII) crystals [KMnO4] in another test tube

o Add some conc. HCl to the KMnO4

o Note what happens. ___________________________________________________

____________________________________________________________________

o What gas is this? ______________________________________________________

o Do you recognise the smell? ____________________________________________

o What effect does it have on blue litmus? ___________________________________

____________________________________________________________________

o Pour the chlorine gas into the potassium iodide and shake.


____________________________________________________________________


o Write an equation for this reaction. _______________________________________

o Can you write the equation in a shorter way? ________________________________

o What has the chlorine done to the iodide ion and what does it tell you about chlorine when compared to iodine? ____________________________________________________________________

____________________________________________________________________

o In a word what has happened to the chlorine? _______________________________

o What is this type of reaction called? ______________________________________

o What type of agent is chlorine? ___________________________________________

Experiment 2b Reaction of Cl2(g) with KBr(aq)


o Test tubeso Potassium manganate(VII) crystalso Conc. Hydrochloric acido Potassium iodide solution o Litmus paper [blue]

Procedure

o Make some chlorine gas as you did in the last experiment by adding conc. Hcl to KMnO4 crystals.

o Pour the chlorine gas into the potassium bromide solution and shake.


___________________________________________________________________

o Write an equation for this reaction. _______________________________________

o Can you write the equation in a shorter way? _______________________________________

o What has the chlorine done to the bromide ion and what does it tell you about chlorine when compared to iodine? ____________________________________________________________________

____________________________________________________________________


o In a word what has happened to the chlorine? _______________________________

o What is this type of reaction called? ______________________________________

o What type of agent is chlorine? ___________________________________________

o How does the colour of bromine compare to that of iodine and chlorine? __________

____________________________________________________________________

o The order of reactivity of non-metals is F- > Cl- > Br- > O2- > I- > SO42-

Experiment 2c Reaction of Cl2(g) with Fe2+(aq)

o Dissolve some Iron(II) sulphate in deionised water

o Make some chlorine as in previous experiments

o Pour the chlorine into the test tube containing the Fe2+ and shake


____________________________________________________________________

o What has happened to the Fe2+? _________________________________________o

____________________________________________________________________

o Write an equation for this. _______________________________________________

Experiment 2d Reaction of Cl2(g) with SO32-

(aq)

o Take some sodium sulphite solution

o Add some barium nitrate solution

o What do you see? _____________________________________________________

o Add HCl and note what happens _________________________________________

o What does this tell us about the solution? ___________________________________

o Take a fresh sample of the sodium sulphite solution

o React it by shaking it with some chlorine gas made as before

o What happens when you add some barium nitrate solution? ____________________

o Add some dilute hydrochloric acid and note what happens. ____________________


____________________________________________________________________

o What has happened to the sulphite? ______________________________________

___________________________________________________________________

Points to note

o OIL RIG Oxidation is Loss Reduction is Gain of electrons

o F is the most reactive

o More reactive element displaces the less reactive element from the solution.



Displacement Reactions of Metals


o Copper sulphate solutiono Magnesium ribbono Test tubes

Procedure

o Put some copper sulphate solution into a test tubeo Add some magnesium ribbono Note what happens

Results

What do you see happening?

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

Why does the solution go colourless?

_____________________________________________________________________

What is the brown substance where the Magnesium ribbon used to be?

_____________________________________________________________________

Write an equation for the reaction

_________________________________________________________________________

What type of reaction is this?

_____________________________________________________________________

What does it tell you about Copper and Magnesium?

_____________________________________________________________________



Place some magnesium in hydrochloric acid

What happens? _____________________________________________________________

_____________________________________________________________________

Name the gas. _______________________________________________________________

What does this tell you about Magnesium and Hydrogen? ____________________________

_____________________________________________________________________

Place some zinc in hydrochloric acid

What happens? _____________________________________________________________

_____________________________________________________________________

Name the gas. ______________________________________________________________

What does this tell you about Zinc and Hydrogen? _________________________________

_____________________________________________________________________

Put some copper into hydrochloric acid

What happens? _____________________________________________________________

_____________________________________________________________________

What does this tell you about copper and hydrogen? ______________________________

_____________________________________________________________________

Arrange copper, magnesium and zinc in order of decreasing activity

_____________________________________________________________________



Tests for Anions in Aqueous Solutions

Phosphate - PO43-

Dissolve some phosphate in water Add some ammonium molybdate solution Add a few drops of conc. HNO3 to ammonium molybdate solution and shake If no reaction heat gently in a water bath Note the result

_________________________________________________________________

_________________________________________________________________

_________________________________________________________________

Nitrate - NO3-1

Dissolve some nitrate in water Add some iron(II) sulphate solution and mix well Hold the test tube at 450 angle Gently pour some conc. H2SO4 down the side It will sink to the bottom Note what happens at the interface of the two layers

_________________________________________________________________

_________________________________________________________________

_________________________________________________________________

Chloride - Cl-1

Dissolve some chloride in water Add some acidified silver nitrate [silver nitrate with nitric acid added] Note what forms and write an equation

_________________________________________________________________

_________________________________________________________________

_________________________________________________________________

Add some ammonia solution and note what happens

_________________________________________________________________


Sulphate - SO42-

Dissolve some sulphate in water Add some barium chloride solution Note what happens and write an equation for the reaction

_________________________________________________________________

_________________________________________________________________

Add some dilute Hydrochloric acid Note what happens

_________________________________________________________________

_________________________________________________________________

_________________________________________________________________

Sulphite - SO32-

Dissolve some sulphite in water Add some barium chloride solution Note what happens and write an equation for the reaction

_________________________________________________________________

_________________________________________________________________

_________________________________________________________________

Add some dilute Hydrochloric acid Note what happens and write an equation for the reaction

_________________________________________________________________

_________________________________________________________________

_________________________________________________________________


Carbonate - CO3

2-

Dissolve some carbonate in water Add some dilute hydrochloric acid solution Note what happens and write an equation for the reaction Test gas produced with lime water Note what happens

_________________________________________________________________

_________________________________________________________________

_________________________________________________________________

Take a fresh sample of carbonate and dissolve it in water Add Magnesium sulphate solution Note what happens and write an equation or the reaction

_________________________________________________________________

_________________________________________________________________

________________________________________________________________

_________________________________________________________________

Hydrogencarbonate - HCO31-

Dissolve some hydrogencarbonate in water Add some dilute Hydrochloric acid Note what happens and write an equation for the reaction Test gas produced with lime water Note what happens

_________________________________________________________________

_________________________________________________________________

_________________________________________________________________

_________________________________________________________________

Add Magnesium sulphate solution Note what happens and write an equation or the reaction

_________________________________________________________________

_________________________________________________________________



Determination of the Relative Molecular Mass of a Volatile Liquid


o Conical flask with tinfoil capo Chloroform, o Water bath, o Torsion balance.

Procedure

o Weigh the “empty” conical flask (full of air) o Put in some chloroform [about1 cm3].o Put flask into boiling water up to its neck until all the chloroform has evaporated o Cool under the tap and then dry.o When all the chloroform has condensedo Re weigh.

o Repeat two more times and take the average mass.

o Convert the volume of the Specific Gravity bottle from the volume at 100oC to STP o Calculate the mass of 22.4 L [22400 cm3] of the chloroform. [at STP]o This gives us the mass of a mole which is the Relative Molecular Mass

Explanation

o At the start the flask is filled with air.o After heating it is filled with CHCl3.o When cooled it is again filled with air (more or less) + a small mass of CHCl3

[mass that filled the bottle.]o The change in mass gives the mass of CHCl3 that filled the bottle of CHCl3 at 100oCo Convert this number of cm3 of chloroform to its STP volume using

P1V1 / T1 = P2V2 / T2

o Mass of chloroform at STP volume should be converted to mass of

22.4 L [22400 cm3] = 1 mole = RMM


Results

• Mass of bottle + air =

• Mass of bottle + air + chloroform =

• Mass of chloroform = y

• Volume of bottle cm3 [V2] = cm3

• Atmospheric pressure [P2] =

• T1 standard temperature = 273 K

• Temperature K ( 273 + water oC) [T2] = 273 + 100 = 373 K

• Volume at STP (V1= P2V2T1/ T2P1) = z

• Mass of z cm3 of chloroform = y

• Mass of 22400 cm3 [22.4 L] = y * 22400 = z

Conclusion

The relative molecular mass of chloroform [CHCl3] is 119.5 [12 +1 + (35.5 * 3)] or methanol CH3OH = 32 [12 +(1*3) +16+1]]

Our experimental value is = ________

% Error = experimental value - actual value * 100 119.5

Sources of error?

_________________________________________________________________________

_________________________________________________________________________

_________________________________________________________________________

_________________________________________________________________________



Preparing a Standard Solution of 0.1 Molar Sodium Carbonate Na2CO3

Apparatus

o Torsion balanceo Spatulao Clock glasso Sodium carbonate decahydrateo Volumetric Flask [250 ml]o Filter funnel o Wash bottle of deionised watero Droppero Beaker [150 ml - for dissolving salt] and 100 [ml for deionised water store]o Stirring rod

Procedure

o Weight out accurately 7.2 g of sodium carbonate

o Put 50 ml of deionised water into a beaker

o Add the sodium carbonate to the beaker with constant stirring

o Wash the last remnants of the sodium carbonate from the clock glass into the beaker using

deionised water

o Keep stirring until all the crystals dissolve

o Using a filter funnel pour the sodium carbonate solution into a volumetric flask

o Wash the beaker and the filter funnel into the conical flask

o Make up to the mark with deionised water [eye level with the mark and the bottom of the

meniscus]

o Stopper and invert 20 times to make the solution homogeneous

o Label with your name, the date, the solution and its concentration

What feature of the volumetric flask makes it accurate? __________________________________

_______________________________________________________________________________

Why did you wash everything into the volumetric flask? ________________________________


_______________________________________________________________________________

Calculations

0.1 Molar [0.1 M] = 0.1 mole of the chemical in 1 Litre of solution

Na2CO3.10H2O = [23*2]+12+[16*3]+10([1*2]+16]) = 286 g

1 mole =286 g

0.1 mole =28.6 g

13.2 g in 1L

= 13.2 /1000 in 1 ml 0.0132 g

= 250 * 0.0132 in 250 ml = g

What are your most likely sources of error? ___________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________


25/ 12/ 09

0.1 M Sodium Carbonate Na2CO3

PJJ

20


To Standardise a Solution of Bench Dilute HCl using a Standard Solution of 0.1 M Sodium Carbonate


o filter funnelo wash bottle of deionised watero retort stand, clamp and white tileo pipettes [20 and 25 ml]o buretteo 150 ml conical flasko methyl orange indicator [SAWBMO - strong acid [HCl] reacting with a weak base [Na2CO3]]o Bench dilute HCl o 0.1 M sodium carbonate solutiono 250 ml volumetric flask

Procedure

Dilute the acid by a factor of 10

o Pipette 20 ml of bench dilute HCl into a 200 cm3 volumetric flask o make up to mark [with deionised water]o invert 20 times [to make homogeneous]

Titration

o Pipette 25 cm3 of Na2CO3 into conical flasko Add a few drops of methyl orange indicator

o Why do you use methyl orange? _______________________________________________

o Note its colour. _____________________________________________________________

o Fill the burette with HCl [ remove air bubble from the neck]o Note the volume in the buretteo Add HCl solution from the burette until the indicator changes colour at the end point

o Note colour of indicator at end point_____________________________________________ o Note the new volume of acid in the buretteo Calculate the volume of acid added when the indicator changes colouro Do one rough and 2 accurate titres. [within 0.1 cm3]o Take the average of the 2 accurate titres


Results and Calculations

Volume of 0.1 M Na2CO3 in flask =

Standard solution of Na2CO3 = M

Rough Accurate 1 Accurate 22nd Reading1st Reading

Titre

Average Titre = [2 accurate]

Equation Na2CO3 + 2 HCl = 2 NaCl + H2O + CO2

1 mole 2 moles nb na

VaMa = VbMb

na nb

Molarity of HCl =

Multiply answer by 10 because we diluted by a factor of 10 before we started

Molarity =

Actual value = 2M


Ma = Vb Mb na

nbVa

22

Va =

Ma =[unknown solution] na =

Vb =

Mb = [0.1 M Na2CO3]nb =

Sources of Error



To Produce a Sample of Sodium Chloride by Reacting Dilute Hydrochloric Acid and Sodium Hydroxide Solutions.


o 25 ml pipette and filler

o Burette and stand

o Conical flask

o White tile

o Indicator – methyl orange or phenolphthalein

o Evaporating dish

o Bunsen burner or hot plate

o 2 M HCl solution

o 2 M NaOH solution

Procedure

Write an equation for the reaction between the HCl and the NaOH

___________________________________________________________

o Pipette 25 ml of NaOH into a conical flask

o Add a few drops of indicator

o What colour does it turn? ______________________________________

o Fill the burette with dilute HCl using a funnel

o Why use the funnel? _________________________________________

o Remove the air bubble from the tip by opening the tap quickly.

o Remove the funnel

o Why did you remove the funnel? _______________________________

o ___________________________________________________________o Add HCl to the conical flask until there is a colour change.

o Note the volume for exact neutralisation_________________________


o Repeat until two values correspond to within 0.1 ml

o Take a fresh sample of NaOH and place in a clean conical flask without any indicator.

o Why do you not add indicator in this case? ________________________

___________________________________________________________

o Add the precise amount of HCl from the burette for exact neutralisation

o Pour the resulting solution into an evaporating dish and heat gently until all the water has evaporated.

o



Determination of the Concentration of Ethanoic Acid in Vinegar


o 0.1 M NaOH standard solutiono A sample of domestic vinegaro Burette, pipette and filler, conical flask, white tile etc. for titrationo Name the indicator will you use. Explain your choice.

____________________________________________________________________________

____________________________________________________________________________

Procedure

o Put 10 ml of vinegar [ethanoic acid] into a 100 ml volumetric flask and make up to the mark with deionised water.

o By what factor have you diluted the vinegar? ______________________________________o Pipette 25 ml NaOH into a conical flasko Add a few drops of indicator.

o What colour is it? _____________________________________________________________

o Why do you add only a few drops of indicator? ____________________________________

____________________________________________________________________________

____________________________________________________________________________

o Place the ethanoic acid into the buretteo Do one rough and two accurate titreso How do you recognise the “end point”? ___________________________________________

____________________________________________________________________________

o To what extent should your accurate titres agree? ____________________________________

Calculate the molarity of the diluted vinegar

EquationCH3COOH + NaOH = CH3COONa + H2O 1 mole 1 mole na nb

Volume of 0.1 M NaOH in flask =


Standard solution of NaOH = 0.1 M

Rough Accurate 1 Accurate 2

2nd Reading

1st Reading

Titre

Average Titre =

VaMa = VbMb

na nb

Calculate the molarity of the undiluted vinegar.

o Multiply you answer to the previous calculation by 10. _______________________________

Express its concentration in % (W/V)

o Molarity = mole / 1000 ml :so divide by 10 to make mole per 100 mlo To convert mole to grams multiply mole by the RMM of ethanoic acid

[12+(1x3)+12+(16x2)+1= 60]

Concentration % (W/V) = Molarity x 60 = 10


Ma = =Vb Mb na

nbVa

27

Va =

Ma [unknown solution] = ?

na =

Vb =

Mb [0.1 M NaOH] =

nb =

Conclusion

Why do you think we diluted the vinegar at the start? ____________________________

_________________________________________________________________________

Sources of error? _________________________________________________________________________

________________________________________________________________________

_________________________________________________________________________

_________________________________________________________________________


Give some uses vinegar

_________________________________________________________________________

_________________________________________________________________________

_________________________________________________________________________

Why is it important to know the concentration of vinegar? ________________________

_________________________________________________________________________

_________________________________________________________________________



To Determine the Number of Molecules of Water of Crystallisation in Hydrated Sodium Carbonate Crystals [Na2CO3.xH2O]


o Clock glasso Stirring rodo Filter funnelo Wash bottle of deionised watero Retort stand and clampo White tileo Pipette [20 or 25 ml]o Buretteo 150 ml conical flasko Methyl orange indicator [SAWBMO - because strong acid [HCl] reacting with a weak base

[Na2CO3]]o 0.25 M HCl or HNO3

o Hydrated sodium carbonate crystals [decahydrate]o 150 ml and 250 ml beaker

Procedure

o Weigh out accurately about 5 g of washing soda crystals on a clock glasso Dissolve these crystals fully in about 100 cm3 of deionised water in a beaker – stir as you add

them.o Transfer solution to 250 cm3 volumetric flask [with washings to ensure all goes in]o Make up to mark [with deionised water]o Invert 20 times [to make homogeneous]o Pipette 25 cm3 of Na2CO3 into conical flasko Add a few drops of methyl orange indicatoro Note its colouro Note the volume in the buretteo Add HCl solution from the buretteo Note the new volume of acid in the buretteo Calculate the volume of acid added when the indicator changes colouro Do one rough and 2 accurate titres. [within 0.1 cm3]o Take the average of the 2 accurate titreso Note colour of indicator at end point


Results and calculations

Mass of washing soda crystals =

Standard solution of HCl = M

Rough Accurate 1 Accurate 22nd

Reading1st

ReadingTitre

Average Titre =

EquationNa2CO3 + 2 HCl = 2 NaCl + H2O + CO2

1 mole 2 moles nb na

Va Ma = Vb Mb

na nb

Molarity of Na2CO3 =


Mb = Va Ma nb

na Vb

30

Va =Ma [Standard Solution HCl] =na =Vb =Mb =nb =

Na2CO3.xH2O we are trying to find the value of x in the formulaI.e. the number of moles of water of crystallisation to each sodium carbonate

Moles of Na2CO3 in 1 L =

Moles of Na2CO3 in 250 ml =

Molar Mass of Na2CO3 =

Mass of Na2CO3 in 250 ml = moles * molar mass =

Mass of water = mass of crystals – mass of Na2CO3 in 250 ml =

Moles of Na2CO3 : Moles H2O

Mass of Na2CO3 : Mass of water RMM Na2CO3 RMM H2O

Value of x in formula =

Correct formula is Na2CO3.10H20

Sources of Error

_______________________________________________________________________

_______________________________________________________________________

_______________________________________________________________________


Molar Mass Na2CO3

31


To Standardise a Permanganate Solution using Ammonium Iron (II) Sulphate Solution [(NH4)2SO4FeSO4.6H2O]

Apparatus required

o wash bottle of deionised watero retort stand and clampo white tileo pipette [20 or 25 ml]o buretteo 150 ml conical flasko 1 M H2SO4

o 150 ml and 100 ml beakero 0.1 molar ammonium iron (II) sulphateo KmnO4 solution

Procedure

o Teacher will make up 0.1 M Mohr’s salto Added dilute sulphuric acid to stop air oxidising Fe2+ to Fe3+ o Pipette 25 cm3 of ammonium iron (II) sulphate into the conical flasko Add 10 cm3 dilute H2SO4 o Why is more acid added here?

___________________________________________________________________________

___________________________________________________________________________

o Note the volume in the burette [measure from top of meniscus because of dark colour]o Add KMnO4 solution from the burette until solution stays permanently pinko MnO4

- acts as its own indicatoro Note the new volume of KMnO4 in the buretteo Do one rough and 2 accurate titres. [within 0.1 cm3]o Take the average of the 2 accurate titres


Standard solution of Ammonium iron (II) sulphate = _______ M


Titre

Average Titre =


EquationMnO4

- + 5Fe2+ + 8H+ = Mn2+ + 5Fe3+ + 4H2O 1 mole 5 moles nb na

Let a = MnO4- Let b = FeSO4

Va Ma = Vb Mb

na nb


Va =

Ma =

na =

Vb =

Mb [Standard Solution (NH4)2SO4FeSO4 ] =

nb =

Moles of KMnO4 in 1 litre = ________ Molar


Ma = Va Ma nb

na Vb

34


To find the amount of Iron [FeSO4] in an Iron Tablet

Apparatus and materials required

o 5 iron tablets [to give an average and make it statistically more accurate]o Pestle and mortaro Wash bottle of deionised watero Retort stand and clampo White tileo Filter funnelo pipette [20 or 25 ml]o buretteo 200 ml volumetric flasko 150 ml conical flasko 1 M H2SO4

o 150 ml and 100 ml beakerso 0.02 M KmnO4 standard solution

Procedure

o Crush five tablets with dilute sulphuric acid using a pestle and mortar

o Why do you crush the tablets? _______________________________________________

o ________________________________________________________________________

o What is the purpose of the acid? ______________________________________________

_________________________________________________________________________

o Transfer with washings using a funnel into a 200 ml volumetric flasko Make up to mark with deionised water – bottom of meniscus and eye level with marko Invert until completely dissolved o Pipette 20 ml into a conical flask using a pipette fillero Add 10 cm3 of dilute sulphuric acid into the conical flask o Why do you use this sulphuric acid ? ___________________________________________

__________________________________________________________________________

o What colour change do you expect?_____________________________________________

o Do 1 rough and 2 accurate titres

o How close should your accurate titres agree? _____________________________________



Standard solution of KMnO4 = 0.02 M


Titre

Average Titre = __________

EquationMnO4

- + 5Fe2+ + 8H+ = Mn2+ + 5Fe3+ + 4H2O 1 mole 5 moles nb na

VaMa = VbMb

na nb


Va =Ma [Standard Solution .02 M MnO4

- ] =

na =Vb =Mb =nb =

Moles of FeSO4 in 1 L =

Moles of FeSO4 in 200 ml =

FeSO4 56 + 32 + (16*4) =

Mass of FeSO4 in 5 tablets = Molarity * RMM = _____ * ______ = _______ g

Mass of FeSO4 in 1 tablet = ________ / 5 = _________ g

Convert to mg per tablet [*1000] = _________ mg

Perfect answer = 325 mg or 300 mg - depends on tablets - value printed on packet

Mass of Iron = 56/152 of ______ mg per tablet = _______ mg


Mb = Va Ma nb

na Vb

37


To Find the Purity of a Sample of Sodium Thiosulphate using a Standard Solution of 0.06 M iodine

This is a Redox titration. What does Redox mean? _____________________________________________________________

_________________________________________________________________________________

What other type of titration do we do? __________________________________________________

Apparatus and Materials

o 0.06M solution of iodine [made by reacting 0.02 M potassium iodate with excess potassium iodide in acid]

o Starch indicatoro Sodium thiosulphate crystals [Na2S2O3.52O]o Dilute sulphuric acido wash bottle of deionised watero retort stand and clampo white tileo pipette [25 ml] and fillero buretteo 250 ml conical flasko 250 ml, 150 ml and 100 ml beakerso Stirring rodo Clock glass

Procedure

o Weigh [about] 6.25g of impure sodium thiosulphate crystals onto clock glasso Transfer crystals to beaker [250 ml] containing about 100cm3 of de-ionised watero Stir and when dissolved transfer to 250cm3 volumetric flask with washingso Make up to mark with de-ionised water - with eye level with mark. o Stopper and invert 20 times.

o Why invert? _________________________________________________________________

o Using a funnel fill burette with sodium thiosulphate solutiono Remove air bubble from tipo Remove funnel in case of dripso Pipette 25cm3 of potassium iodate into the conical flasko Use graduated cylinder to add 20cm3 of dilute sulphuric acid, followed by 10cm3 of 0.5M

potassium iodide solution from 100 ml beaker to the conical flask.

o Why do you add these two compounds? ___________________________________________


____________________________________________________________________________

o What colour does the solution become? ________________________________

o Titrate. Until pale yellow.

o Add a few drops of starch indicator.

o What do you observe? ______________________________________________

o What does this colour tell you about the solution in the conical flask?

_________________________________________________________________

o Why do you add the starch at this point and not earlier?

_________________________________________________________________

_________________________________________________________________

o Continue adding thiosulphate solution drop by drop until blue colour disappears, to give colourless solution. Note the titration figure.

o Do one rough and 2 accurate titres. [within 0.1 cm3]

o Take the average of the 2 accurate titres

o Calculate the concentration of the thiosulphate solution on moles per litre


Standard solution of iodine (I2) = 0.06 M


Reading1st

Reading

Titre

Average Titre = ______________ (of two accurate)


Calculate the concentration of the thiosulphate solution

Equation I2(aq) + 2 S2O32-

(aq) = 2 I- (aq) + S4O62-

(aq)

1 mole 2 moles na nb

Va Ma = Vb Mb

na nb


Va =

[Standard Solution I2 ] Ma = na =

Vb =

Mb =

nb =

Moles of Na2S2O3 in 1 L = _______ M

Calculate the purity of the sample of thiosulphate

Moles of Na2S2O3 in 250 cm3 = ¼ [250/1000] of above =

Mass of 1 mole of Na2S2O3.5H2O = [RMM] = (23 x 2) + (32 x 2) + (16 x 3) + 5 (18) =

Mass of Na2S2O3.5H2O in sample = moles x RMM =

% Purity = Mass of Na2S2O3.5H2O in solution x 100 = Mass of crystals

Neither iodine nor thiosulphate are primary standards.

What does primary standard mean? _________________________________________

______________________________________________________________________

What type of standards are they? ___________________________________________

Explain why each is not a primary standard.

______________________________________________________________________

______________________________________________________________________

______________________________________________________________________


Mb = Va Ma nb

na Vb

41

______________________________________________________________________



To Determine the Percentage (W/V) of Sodium Hypochlorite in Bleach

Introduction

Many commercial bleaches are solutions of sodium hypochlorite [NaOCl] or calcium hypochlorite [Ca(OCl)2]The bleach is diluted to bring its concentration into a suitable range, and then it is reacted with excess potassium iodide in the presence of acid. This generates iodine solution of the same concentration as the hypochlorite.

ClO1-(aq) + 2I-

(aq) + 2 H+(aq) = Cl-

(aq) + I2(aq) + H2O(l)

The iodine solution is then titrated against a standard solution of 0.1 M sodium thiosulphate to find its concentration

I2(aq) +2 S2O32-

(aq) = 2 I-(aq) + S4O6

2-(aq)


o Bleach [NaClO] solution (fresh)o Potassium iodide solutiono Dilute sulphuric acido 0.1 M sodium thiosulphate solutiono Starch solutiono Deionised watero Titration apparatus

Procedure

Diluting the bleach

o Pipette 25 ml of bleach solution into the 250 ml volumetric flasko Make up to the mark with deionised watero Bottom of meniscus level with marko Eye level with mark when readingo Stopper in invert 10 times

o Why invert the flask? ________________________________________________________

__________________________________________________________________________

o Why dilute the bleach? _______________________________________________________

___________________________________________________________________________


Doing the titration

o Pipette 25 ml of diluted bleach solution into the conical flask using the pipette and fillero Add 10 cm3 of dilute sulphuric acid to the flasko Add 1 cm3 (excess) of concentrated KI to flask to ensure all ClO1- is converted to Iodine

o What do you see happening when you add the KI? _________________________________

__________________________________________________________________________

o What is formed that causes this? ________________________________________________

o Using a funnel fill the burette with sodium thiosulphateo Remove bubble from necko Remove funnel. Explain why. __________________________________________________

___________________________________________________________________________

o Do one rough and two accurate titres [within 0.1 ml]o Add starch indicator when the solution is straw colouredo Why add the starch at this point? ______________________________________________

__________________________________________________________________________

o How do you recognise the end point of the titration? ________________________________

___________________________________________________________________________

Results

Standard solution of thiosulphate = 0.1 M


Reading1st

Reading

Titre

Average Titre = (of two accurate)


Calculate the concentration of the iodine solution

Equation I2(aq) + 2 S2O32-

(aq) = 2 I- (aq) + S4O62-

(aq)

1 mole 2 moles na nb

Va =

Ma =

na =

Vb =

Mb =

nb =

Va Ma = Vb Mb

na nb

Moles of I2 in 1 L = M

Moles of hypochlorite = moles of iodine =

Molarity of hypochlorite =


Ma = Vb Mb na

nb Va

45

Calculate the concentration of the undiluted hypochlorite solution

Molarity of bleach x 10 to allow for dilution = ______________________________________

Calculate percentage (%W/V) [mass per 100cm3]

o What is the RMM of NaClO? _______________________________________________

o How many grams are there in a litre [1000 ml] of the solution?

M x RMM = __________________________________________________

o How many grams are there in 100 ml? ________________________________________

o % (W/V) =



Determination of the Heat of Reaction of HCl(aq) with NaOH(aq)


o 2 polystyrene cupso Two 100 ml graduated cylinderso 1 accurate [0.1 oC] thermometero 1 M HClo 1 M NaOH

Procedure

HCl + NaOH = NaCl + H2O

o Using a graduated cylinders place 100 ml of 1.0 M HCl into one polystyrene cup [0.1 mole]

o Using another cylinders place 100 ml of 1.0 M NaOH into the other polystyrene cup [0.1 mole]

o Why do we use polystyrene cups? _______________________________________________

___________________________________________________________________________

o Measure the temperature of each solution [wash thermometer between measurements]

o Calculate the average temperature and record as starting temperature

o Carefully mix the two solutions and record the maximum temperature as final temperature.

o Calculate the heat produced using h = mcθ


Temperature of acid =

Temperature of base =

Starting Temperature =

Final temperature =

Temperature rise [θ] =

Mass = 200 g = 0.2 kg

Specific Heat capacity = 4.2 kJ / kg / oC© Peter J Jackson 2012

[100 ml + 100ml = 200 ml = 200g assuming density of salt solution is same as density of water]

47

Heat produced h = mcθ

= 0.2 * 4.2 * θ

= 0.2 * 4.2 * _____

= ________ kJ

This was when 0.1 mole reacted so when 1 mole reacted = 10 * h

Divide by 1000 to give answer in kJ _______________

Actual Value = -57 kJ mol-1

Sources of error

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________



P.T.O

48


Preparation and Properties of Ethyne


o Calcium dicarbide(carbide)o Watero Acidified copper (II) sulphate solutiono Acidified potassium permanganate solutiono Bromine water

Procedure

o Set up the apparatus as shown in the diagram

o What does the calcium dicarbide look like? ___________________________________________

_______________________________________________________________________________

o Drop water onto the calcium dicarbide slowly.

o What do you see happening? ______________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

o What is the purpose of the acidified copper sulphate? ____________________________________


o Give two examples and their sources. ________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

o What does the ethyne smell like? ____________________________________________________

o What colour is the ethyne? _________________________________________________________

o Is it soluble in water? Explain your answer. ___________________________________________

_______________________________________________________________________________

o Collect three test tubes full of ethyne.

o Light one test tube

o What do you observe? ____________________________________________________________

______________________________________________________________________________

o Put some acidified KMnO4 into another test tube and shake. Note what happens. _____________

_______________________________________________________________________________

o What does this tell us about ethyne? _________________________________________________

o Put some bromine water into another test tube and shake. Note what happens. _______________

_______________________________________________________________________________

o What does this tell us about ethyne? _________________________________________________

o Give two everyday uses of ethyne. __________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________o



Rate of Production of Oxygen using MnO2 as a Catalyst

Introduction

Rate is the change in concentration per unit timeWe will measure the amount of product by the volume of gas e.g. 100 cm3 produced in 5 minutes = 20 cm3 per minute [overall rate]However the rate of this reaction varies as time goes on – it gets slower. We can see this easily.This experiment will show us how to measure the rate at any given time – this is called the instantaneous rate as opposed to the overall rate.

Apparatus

300ml conical flask, delivery tube, special bends, 800ml beaker, 100ml measuring cylinder, 20 volume hydrogen peroxide, half a teaspoon MnO2 (precipitated).

Procedure

Set up as shown.

o Place 20cm3 of fresh H2O2 in a conical flask and add about 50 cm3 water

o Place a small half spatula of MnO2 at the neck of the flask and fit the bung. Make sure that no peroxide is trapped between the stopper and the flask or gas will escape.

o When organised sit the flask on the bench and start timing - swirl for 5 sec.

o Note the volume of gas produced every 30 sec.

o As soon as the volume is noted swirl the flask for another 5 sec.

o Repeat until no more gas is produced.



MnO2

H2O2(aq) =======> H2O(l) + 1/2O2(g)

Draw up a table of time and volume produced.

Time Volume Time Volume Time Volume Time Volume00.30 04.00 07.30 11.0001.0 04.30 08.00 11.3001.30 05.00 08.30 12.0002.00 05.30 09.00 12.3002.30 06.00 09.30 13.0003.00 06.30 10.00 13.3003.30 07.00 10.30 14.00

o Draw a graph of volume against time. [opposite page]

o Calculate the instantaneous rate at two points marked A [1 minute] and B [6 minutes]:

a) Calculate average rate = volume = time

b) Draw a tangent at the point A [ do B when finished A]

b) Construct a horizontal and a vertical line to intersect the tangent.

c) Measure the slope of the tangent

Instantaneous rate = Rise (volume) = cm3 min-1

Run (time)

What is the difference between the rate at A, and the rate at B? ___________________________

_____________________________________________________________________________

Can you suggest why this is so? ___________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

Conclusion

Rate decreases as the reaction proceeds because the concentration of a reactant (H2O2) decreases.



Effect of Concentration on Reaction Rate using Sodium Thiosulphate and Dilute Hydrochloric Acid

Apparatus

o 50 ml conical flasko 10 ml and 50 ml graduated cylindero Bench dilute HClo Sodium thiosulphate solution [0.1 M]o Deionised water o Piece of paper with a cross marked on ito Stopwatch

Procedure

o Place 50 ml of 100% sodium thiosulphate solution in the conical flasko Place the flask on the crosso Add 10 ml of dilute HCl and start timing immediatelyo Note the time taken for the cross to disappear [i.e. for the solution to become so creamy that

you cannot see the cross through it.]o Empty the flask and wash it immediately [to prevent staining] - then dry outside of flasko Repeat using 80%, 60%, 40%, 20%, 0% sodium thiosulphate solutiono Record results on tableo Draw a graph of rate [vertical axis] against concentration [horizontal axis]

S2O32-

(aq) + 2 H+(aq) = S(s) + SO2(g) + H2O(l)

Results

Recipe[vol. thiosulphate :vol. water]

Concentration[% thiosulphate]

Time in seconds[for cross to disappear]

Rate [1000/time]to give integers

50 ml S2O32- : 0 ml H2O 100

40 ml S2O32- : 10 ml H2O 80

30 ml S2O32- : 20 ml H2O 60

20 ml S2O32- : 30 ml H2O 40

10 ml S2O32- : 40 ml H2O 20

0 ml S2O32- : 50 ml H2O 0


Why does the solution go cloudy? __________________________________________________

What is a colloidal solution? ______________________________________________________

______________________________________________________________________________

What do you call a solid formed when two liquids mix? _________________________________

Graph


Conclusions

What type of graph is this? ________________________________________________________

What is the effect of concentration on the rate of the reaction? ____________________________

_______________________________________________________________________________

_______________________________________________________________________________

What do we mean by rate of reaction? ________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________



Effect of Temperature on Reaction Rate using Sodium Thiosulphate and Dilute Hydrochloric Acid

Apparatus

o 50 ml conical flasko 10 ml and 50 ml graduated cylindero Bench dilute HClo Sodium thiosulphate solution [0.1 M]o Piece of paper with a cross marked on ito Stopwatcho Water batho Thermometer

Procedure

o Place 50 ml of 100% sodium thiosulphate solution in the conical flasko Place the flask in a water bath and heat to 70oCo Remove the flask and dry it quicklyo Place the flask on the crosso Add 10 ml of dilute HCl and start timing immediatelyo Note the time taken for the cross to disappear [i.e. for the solution to become so creamy that

you cannot see the cross through it.]o Empty the flask and wash it immediately [to prevent staining] - then dry outside of flasko Repeat at 60oC, 50 oC ; 40 oC , 30 oC; 20 oC [doesnt have to be exact – record actual temp.]o Record results on tableo Draw a graph of rate [vertical axis] against temperature [horizontal axis]

S2O32-

(aq) + 2 H+(aq) = S(s) + SO2(g) + H2O(l)

Results

Temperature[oC ]

Time in seconds[for cross to disappear]

Rate [1000/time]to give integers

70

60

50

40

30

20


Why does the solution go cloudy? __________________________________________________

What is a colloidal solution? ______________________________________________________

______________________________________________________________________________

What do you call a solid formed when two liquids mix? ________________________________

Graph


Conclusions

What type of graph is this? ________________________________________________________

What is the effect of temperature on the rate of the reaction? ____________________________

_______________________________________________________________________________

_______________________________________________________________________________

What do we mean by rate of reaction? ________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________


Draw Buchner filter apparatus


Recrystallisation of Benzoic Acid and Determination of its Melting Point Introduction

o Recrystallisation is the most common method of separating a solid material from solid impurities

o Called recrystallisation because we start with impure crystals, dissolve them and then form pure crystals again.

o Substances dissolve more easily in hot liquids than in coldo Benzoic acid is very soluble in hot water but only slightly soluble in coldo Solvent is the liquid in which the substance is dissolvedo Solute is the substance dissolvedo Solution is in the mixture of solute and solvento The benzoic acid is dissolved in the minimum amount of hot watero To get a solution that is almost saturated at the boiling point of the solvento This hot almost saturated solution is filtered to remove any insoluble impurities using a hot

buchner filter. The insoluble impurities are caught in the filter paper and are called the residue

o The benzoic acid and soluble impurities pass through the filter paper and are collected. This solution is called the filtrate

o When the hot solution cools the benzoic acid recrystallises in pure formo Any soluble impurities remain in solution due to their much lower concentration compared

to the benzoic acid

Apparatus

o Büchner Flasko Büchner Funnelo Filter Pumpo Benzoic acid [with charcoal as insoluble impurity and

sodium chloride as soluble impurity]o Hot plateo Aluminium block and thermometer with oil o [or Melting point apparatus]o Hot watero Ice bath

Procedure

Dissolve the impure benzoic acid in the minimum of hot water

o Place about 1.5 g of impure benzoic acid into a beaker

o Add about 10 ml of water

o Boil gently© Peter J Jackson 2012 60

o Add 10 ml units of water and boil until all the acid has just dissolved

Remove the insoluble impurities

o Heat a buchner filter in hot water

o Switch on the filter pump

o Pour the liquid into the filter

o What is left in the filter paper? ______________________________________________

o What type of impurity is this? ______________________________________________

o What has passed through the filter paper? _____________________________________

o Why did you heat the buchner filter before use? ________________________________

_______________________________________________________________________

o Discard the filter paper and residue.

Remove the soluble impurity

o Cool the flask containing the filtrate rapidly in an ice bath

o When crystals form pour the contents of the flask through a gravity filter

o If necessary wash the crystals out of the flask using filtrate – not water

o What are the crystals? ____________________________________________________

o What is in the filtrate in this case? __________________________________________

o Wash the crystals with a tiny amount of cold deionised water.

o Explain why you do this. __________________________________________________

__________________________________________________________________________

Check the purity of your sample

1. Place the aluminium block on the hot plate and turn on the heat gently

2. Place a tiny sample of benzoic acid in the centre of the block


3. Place a 0.1oC thermometer into the hole with some mineral oil

4. What was the purpose of the mineral oil? ______________________________________

5. Note the temperature at which the benzoic acid begins to melt. _____________________

6. Note the temperature at which it is all melted. ___________________________________

7. Is your sample pure? ______________________________________________________

Check that your sample is in fact benzoic acid

o Take a fresh sample of pure benzoic acid and mix it with your sample

o Check the melting point again

o Is the melting point of the mixture the same as the pure substance? __________________

________________________________________________________________________

o What does this tell you about your sample of benzoic acid? ________________________

________________________________________________________________________


Draw apparatus


Making Soap

Apparatus

o Green Organic Chemistry Apparatus tray

o NaOH pelletso Ethanolo Sunflower oilo Brineo Hard watero Deionised watero Filter funnelo Beakerso Water bath and hot plate

Procedure

o Reaction is called Saponification [alkaline hydrolysis]

o Into a 100 ml pear shaped flask pour

o 20ml sunflower oil [or any fat or oil]

o Add 3 g of NaOH pellets [caution – very caustic]

o Add 30 ml ethanol to dissolve the fat

o Add some anti-bumping granules

o Boil under reflux for 30 min. as reaction is slow

o Reflux prevents loss of vapour from the apparatus during boiling

o From time to time swirl flask to remove substances [Na salts of fatty acids and un-

hydrolysed fat] stuck to side of flask

o Cool

o Rearrange apparatus for distillation

o Distil off most of the ethanol [about 20ml] to make it easier to isolate the soap

o Pour some brine [concentrated sodium chloride solution]into a 150 ml beaker

o Pour contents of flask into concentrated NaCl solution

o What do you see happening and what is this called?

_________________________________________________________________________


_________________________________________________________________________

o Soap does not dissolve in salt solution so it precipitates out [called salting out]

o What happens to the excess NaOH solution?

_________________________________________________________________________

_________________________________________________________________________

o Filter off the soap

o Wash with salt solution

o Write an equation for the reaction that has occurred

_________________________________________________________________________

_________________________________________________________________________


o Remove a sample of the soap and mix with deionised water in a test tube

o Shake vigorously

o Note what happens:

_________________________________________________________________________

_________________________________________________________________________

o Add some soap to hard water

o Shake vigorously

o Note what happens

_________________________________________________________________________

_________________________________________________________________________

o Commercial soap has colour and perfume added

o Why does soap burn your eyes?


_________________________________________________________________________

_______________________________________________________________________


Preparation and Properties of Ethene

Apparatus

o Green Tray of Organic Apparatuso Glass wool Retort stand and clampo Ethanol 4 test tubes, stoppers and racko Aluminium oxide powder bunsen burnero Bromine watero Acidified KMnO4 solution

Procedure

o Pour about 2 cm depth of ethanol into a test tube

o Push in enough glass wool to soak up the ethanol

o Why do you put the glass wool in after the ethanol? _________________________________

___________________________________________________________________________

o What was the purpose of the glass wool? ____________________________________________

____________________________________________

____________________________________________

o Set up the apparatus as shown in the diagram


Aluminium oxide

Glass wool and ethanol

65

o What is the function of the aluminium oxide? _______________________________________

o Describe its appearance ________________________________________________________

o Write an equation for the production of ethene in this experiment.

____________________________________________________________________________

o Discard the first test tube collected

o Why? _______________________________________________________________________

o Collect a few tubes of ethene by displacement of water [over water] and stopper them

o When the reaction is finished remove the tube from the water before you stop heating

o Why do you remove the tube from the water before you stop heating? _____________________

______________________________________________________________________________

Properties

o Ignite a test tube of ethene

o What do you observe? ___________________________________________________________

______________________________________________________________________________

o Add a few drops of lime water to the test tube and shake it.

o What do you see? _______________________________________________________________

o Write an equation for the combustion of ethene _______________________________________

o Add some bromine water to a test tube of ethene and shake

o What do you see? _______________________________________________________________

o What does this tell you about ethene? _______________________________________________

o Add some acidified KMnO4 solution to a test tube of ethene and shake

o What do you see? _______________________________________________________________

o What does this tell you about ethene? _______________________________________________


Additional activities

o Is ethene soluble in water? Explain your answer. ______________________________________

______________________________________________________________________________

o List three uses of ethene [ it is not a fuel! Use the internet]

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________


Preparation and Properties of Ethanal


o Green Tray of Organic Apparatus

o Sodium Dichromate crystals

o Spatula

o Torsion balance

o Ethanol

o Conc. Sulphuric Acid

Prepare sulphuric acid in pear shaped flask

o Pour 6 cm3 of deionised water into flask

o Add 2 cm3 of conc. H2SO4 – swirl and cool

o Add a few Anti-bumping Granules to the flask

o Clamp in position

Prepare the ice-bath [ethanal is volatile and this stops it evaporating]

o Put some ice cubes in a 400 ml beaker

o ¾ fill with cold water


Make up sodium dichromate/alcohol solution

o Weigh out 5 g

o Put in small beaker

o Add 5 cm3 deionised water

o Add 4 cm3 ethanol

o Stir until dissolved

o Place sodium dichromate/ethanol in dropping funnel

o Turn on the condenser water supply

Set up apparatus as in diagram

o Heat the sulphuric acid until it boils

o Remove heat

o Add sodium dichromate from dropping funnel slowly so that the

o mixture a few minutes after all dichromate has been added

Ethanal contains impurities which should be removed

o Water

o removed by shaking with anhydrous sodium carbonate for a few minutes and

o then filtering off the crystals which have absorbed the water

o Ethanol and possibly ethanoic acid

o Remove by distilling the mixture

o Collect the fraction that distils between 20 – 23oC

Note and explain the colour change as the reaction proceeds

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

Why is the ethanal collected in an ice bath?

_____________________________________________________________________________________


Describe the smell of ethanal.

_____________________________________________________________________________________

Which substance is in excess? Explain why.

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

Further Activities

Fehling’s Testo Mix some Fehling’s A and B solutions

o Add some ethanal

o Heat in a water bath for a few minutes

o Note and explain what happens

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

Tollens Silver Mirror Test

o Make some Ammoniacal silver nitrate

o Place about 2 cm3 in a clean test tube

o Add some ethanal

o Heat in a water bath

o Note and explain what you see happening

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________© Peter J Jackson 2012 69

_____________________________________________________________________________________

Acidified Potassium Permanganateo Place some very dilute acidified Potassium permanganate in a test tube

o Add some ethanal

o Heat in a water bath

o Note and explain what happens

_____________________________________________________________________________________

_____________________________________________________________________________________

____________________________________________________________________________________

_____________________________________________________________________________________



Production and Properties of Ethanoic Acid


o Green Organic Practical Trayo Teat Pipetteo 2 * 10 ml measuring cylinders [1 for H2SO4 and 1 for alcohol

& water]o Test tube rack plus 5 test tubeso Water batho Conc. H2SO4

o Sodium Dichromate crystals [Na2Cr2O7]o Deionised water [wash bottle]o CaCO3 powdero Mg ribbono Ethanolo Litmus Paper

Safetyo Wear safety glasseso Conc. H2SO4 is corrosive and reacts exothermically with

water

Procedureo Pour in 6 cm3 deionised water into a Pear Shaped flasko Add 3.5 cm3 of Conc. H2SO4 – makes diluteo Mix and cool

o Why? __________________________________________

_______________________________________________

o Add 9g sodium dichromate to the diluted acid

Is this the limiting reagent?________________________________________________________

_________________________________________________________________________________

o Add a few anti-bumping granules

What do anti-bumping granules do? ________________________________________________

______________________________________________________________________________

o Clamp flasko Insert Liebig condenser for refluxo Clamp condenser


Sand bath

Hot plate

71

o Add side-arm connector [to prevent pressure build up if gas forms quickly – don’t draw]o Pour 10 cm3 water into a dropping funnel

o Add 2 cm3 of ethanol

o Place the reaction vessel into a beaker of cold water

Why? _________________________________________________________________________

o Slowly add the alcohol/water mixture so that it does not react too vigorously.

o When all the alcohol/water mixture has been added heat for 20 minutes under reflux

o What is the purpose of reflux ______________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

o Note and explain the colour change __________________________________________________

_______________________________________________________________________________

o Remove the water bath and allow apparatus to cool a little

o Rearrange the condenser for distillation

o Place a thermometer in top of the side-arm

o Place sand-bath under reaction vessel

o Why is boiling water not used? _____________________________________________________

_______________________________________________________________________________

o Collect about 15 cm3 of dilute ethanoic acid

o A little ethanal may be present as an impurity. Water, ethanol and ethyl ethanoate may also be

present

Reaction Equation ______________________________________________________________

Name the impurities and describe how to remove them. _________________________________

_______________________________________________________________________________

_______________________________________________________________________________

______________________________________________________________________________


_______________________________________________________________________________

Further Activities

Note the smell of ethanoic acid _______________________________________________________

Test it with moist litmus ________________________________________________________

Reaction with a carbonate [Calcium Carbonate]

o Place some calcium carbonate powder in a test tube

o Add some dilute ethanoic acid

o Note what happens and write an equation

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

Reaction with Magnesium

o Place some dilute ethanoic acid in a test tube and add a clean piece of Mg ribbon

o Note what happens and write an equation

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

Reaction with Ethanol

o Place about 1 cm3 of concentrated ethanoic acid [Glacial ethanoic acid] in a test tube and add 1 cm3 of ethanol then carefully add 10 drops of conc.H2SO4.

o Heat test tube gently in a moderate water bath for a few minutes.

o Smell the product and write an equation.

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________



Extraction of Clove Oil from Cloves [or similar] by Steam Distillation

Introduction

Natural products are very useful but until recently we had to take them along with much of the plant or animal that they came from.Modern separation techniques allow us to extract the pure substanceMany have pharmaceutical applications. Examples are morphine, aspirin, quinine, nicotine, cocaine, caffeine etc.One of the processes is steam distillationIt is used because direct distillation would require a temperature so high that it would damage the clove oil


o 5 – 10 g of whole cloveso Anti-bumping granuleso PVC gloveso Steam Generatoro Water bath

Procedure

Seam Distillationo Set up the apparatus

as shown

o Place 5 – 10 grams of cloves in the pear shaped flask

o Cover them with a little warm water

o Connect the steam generator such that there is a constant steady supply of steam

o Make sure there is a vertical tube connecting directly to the atmosphere.


o Why is this necessary? _______________________________________________________

___________________________________________________________________________

___________________________________________________________________________

o Collect the distillate.

o What colour is it? _____________________________________________________________

o Describe its smell. ____________________________________________________________

o When sufficient distillate has been collected disconnect the steam generator before you stop heating.

o Why? ______________________________________________________________________

____________________________________________________________________________

o Why did you wear PVC gloves? _________________________________________________

____________________________________________________________________________

____________________________________________________________________________

Solvent Extraction

o Place the distillate in a separating funnel

o Add some cyclohexane or other suitable solvent and shake steadily

o Why is cyclohexane a suitable solvent ? ___________________________________________

____________________________________________________________________________

o The top layer is the clove oil [eugenol] in cyclohexane

o Evaporate off the cyclohexane on a hot plate in a fume cupboard

Other points

o Give two uses of clove oil.

_________________________________________________________________________

_________________________________________________________________________

_________________________________________________________________________



Separation of a Mixture of Indicators by Chromatography

Apparatus

o Chromatopot [jam jar]o Chromatography Papero Solvent [alcohol]o Mixture of indicatorso Acid / alkali for development

Procedure

o Draw a line across the chromatography paper about 1 cm from the

bottom

o In the middle of this line spot the mixture of indicators using a capillary

tube

o Allow the spot to dry and then spot again at the same point

o Repeat several times

o Dip the paper into the solvent - making sure the spot stays above the

solvent

o Allow to stand until solvent gets near the top

o Remove paper and allow to dry

o Draw what you see on the diagram opposite

Conclusion

o This is a useful method of separating substances in solution

o Each substance moves a particular distance compared to the solvent front

o This is called the Chromatographic Index

C. I. = Distance moved by substance Distance moved by solvent front

Chromatography A separation technique where a mobile phase moves in contact with a stationary phase causing the substances to separate.


Solvent

77


To show the effect of Concentration on an equilibrium mixture

Apparatus

o Test tubes and racko Deionised water in 150 ml beakero Dilute hydrochloric acido Dilute sodium hydroxideo Potassium dichromate crystalso 2 teat pipettes

Procedure

o Quarter fill a test tube with deionised water

o Add a spatula of potassium dichromate crystals and dissolve

o Note the colour of the solution _________________________________________________

o Slowly add sodium hydroxide solution using a pipette until something happens.

o Note what happens. ___________________________________________________________

____________________________________________________________________________

o Now add some dilute hydrochloric acid using a pipette until something happens

o Note what happens. ___________________________________________________________

o Slowly add sodium hydroxide solution using a pipette until something happens.

____________________________________________________________________________

o Etc.

o Draw a diagram of the experiment.


Results

Cr2O72- + H2O = 2 CrO4

2- + H+

Dichromate Chromate Orange Yellow

When we added NaOH the solution went yellow

When we added HCl the solution went orange

Explanation

Add Sodium hydroxide

The sodium hydroxide reacts with the H+ to form water [ H+ + OH- = H2O ]Therefore the H+ concentration dropsAccording to Le Chatelier the system will try to get it back to its original level How? By making more H+

It does this by reacting dichromate with water forming chromate and H+

The orange colour fades as the dichromate is used up and the yellow colour increases as the chromate forms

Add HCl

The H+ conc. increases [acid]According to Le Chatelier the system will try to get it back to its original level How? By using up the extra H+ How does it do this? It does it by reacting the H+ with chromate to form dichromateAs the chromate changes to dichromate the yellow colour fades and the orange colour increases

Cr2O72- + H2O = 2 CrO4

2- + H+

Dichromate Chromate Orange Yellow

Conclusion

Le Chatelier’s Principle

If any of the factors influencing a reversible reaction at equilibrium is changed then

the system will react in such a way as to diminish that change.



To Show the Effect of Temperature on an Equilibrium Mixture


o Test tubes and racko Deionised watero Cobalt chloride crystalso Conc. HCl

Procedure

Exothermic

CoCl42- + 6 H2O = Co(H2O)6

2+ + 4 Cl-

Endothermic Blue Pink

Preparation

o Quarter fill a test tube with deionised water

o Add a spatula of cobalt chloride crystals

o Note the colour of the solution __________________________________________________

o Explain why it is this colour ____________________________________________________

____________________________________________________________________________

____________________________________________________________________________

o Add conc HCl until the solution changes colour

o What colour is it now?_________________________________________________________

o Explain the colour change.______________________________________________________

____________________________________________________________________________

____________________________________________________________________________

o Add water until an intermediate colour is formed.


Experiment

Place the test tube in hot water

Note and explain what happens. ____________________________________________________

____________________________________________________________________________

____________________________________________________________________________

Place the test tube in iced water

Note and explain what happens. ____________________________________________________

____________________________________________________________________________

____________________________________________________________________________

Results

The intermediate colour is purple

When we placed it in hot water it turned Blue

When we place it in iced water it turned Pink

Explanation Exothermic

CoCl42- + 5 H2O = Co(H2O)6

2+ + 4 Cl-

Endothermic Blue Pink

Add Heat

o The temperature rises

o According to Le Chatelier’s Principle the system will try to get it back to its original level

o System tries to lower it.

o How? By using it up [doing the endothermic reaction i.e. to the left]

o As the Co(H2O)62+ changes to CoCl4

2- the pink colour fades and the blue increases


Cool

o The temperature drops

o According to Le Chatelier’s Principle the system will try to get it back to its original level

o System tries to raise it.

o How? By creating heat [doing the exothermic reaction i.e. to the right]

o As the CoCl42- changes to Co(H2O)6

2+ the blue colour fades and the pink increases.

Conclusion

Le Chatelier’s Principle

If any of the factors influencing a reversible reaction is changed then the

system will react in such a way as to diminish that change.

At equilibrium / reversible reactions / oppose / applied stresses.



Colorimetric Estimation of the Amount of Free Chlorine in Bleach .

Introduction

o The intensity of a colour in solution is directly proportional to its concentration.o A colorimeter passes light of a particular wavelength through the solution and measures the

amount of light absorbed by the solutiono If the absorbance is measured for a range of concentrations of the coloured substance being

studied then a calibration curve can be draw. This is a graph of absorbance against concentration.o If the absorbance of a solution of unknown concentration is found its concentration can be found

using the calibration curve. o Chlorine compounds are used to kill micro-organisms in swimming poolso The active ingredients are usually HOCl [chloric(I) acid] and its conjugate base ClO- the chlorate

(I) ion. These two compounds together make up what is called Free Chlorine.o These ions react with iodide ions in the same way as chlorine does by oxidising the to iodine

o Cl2(aq) + 2 KI (aq) = I2(aq) = 2 KCl(aq)

o The more concentrated the chlorine in water, the more intense the colour of the iodine solution formed

o A sample of diluted bleach is reacted with potassium iodide and is compared to a calibration curve produced by reacting solutions of known concentration with the same potassium iodide

Precautions

Wear safety glasses


2% potassium iodide solution5% ethanoic acid in water solutionSample of diluted bleachMilton sterilising fluidDeionised waterColorimiter440 nm wavelength filterCuvettes50 cm3 volumetric flasks with stoppersBurettes250 cm3 volumetric flasks10 cm3 measuring cylinders


Procedure and Results

Setting up the colorimeter

o Place 2.5 ml of fresh Milton into a 250 cm3 volumetric flask and make up to the mark with

deionised water

o Label five 50 ml volumetric flasks A, B, C, D and E respectively

o Place 5 cm3 of 5% ethanoic acid solution into each

o Use a burette to transfer the diluted Milton solution to the labelled volumetric flasks as

follows

1 cm3 to flask B

2 cm3 to flask C

4 cm3 to flask D

8 cm3 to flask E

o Transfer 5 cm3 of KI solution [i.e. an excess] to each flask and fill to the mark with

deionised water.

o Stopper the flasks and mix thoroughly by inverting

o Allow about five minutes for the free chlorine in the bleach to oxidise the iodide ions to

iodine.

o Colours of different intensities should be apparent and correspond with the following

concentrations in each flask

Flask A B C D E

Concentration of I2 in ppm 0 4 8 16 32

Absorbance

o Switch on the colorimeter and place a 440 nm filter in the filter slot

o Fill in the five solutions into a cuvette after first rinsing each cuvette with the solution it is

going to contain.

o Zero the calorimeter as per instructions

o Measure and record the absorbance of each concentration in the above table

o Draw a graph, called a calibration curve, of absorbance against concentration on the

paper provided


The experiment propero In a 50 cm3 flask labelled F place 5 cm3 of 5% ethanoic acid and then 5 cm3 of 2%

potassium iodides solution and fill to the mark with diluted bleach. Once again allow five

minutes for the colour to develop.

o Place a sample of this solution in a fresh cuvette and using the colorimeter measure and

record the absorbance of this solution.

o Using the graph find the concentration of NaOCl

o Multiply by 71/74.5 [Cl2/ NaOCl] to find the concentration of free chlorine in the sample.

Conclusions © Peter J Jackson 2012 85

Colorimetry can be used to find the concentration of lead or fertilisers in water as well as the concentration of free chlorine in swimming pools


To Determine the Total Suspended and Dissolved Solids in a Sample of Water.

Precautions

Wear safety glasses

1 To Determine the Amount of Suspended Solids in a Sample of Water


o Filter paper, o Filter funnel o river water, o torsion balance, o measuring cylinder,


Dry filter paper in oven at 100oC for several hours [mark the paper so you know its yours]

Weigh dry paper = _________

Fold paper and place in filter funnel

Pour 200 ml through paper.

Place wet paper in oven at 100oC and leave for several hours

Reweigh paper = _________

Dissolved solids in 200 ml = paper after filtering – paper before filtering = _________

Dissolved solids in 1 litre = _________

Express in mg l-1 (p.p.m.) =

Conclusions


2 To Determine the Amount of Dissolved Solid in a Sample of Water


o Filtered water, o 400 ml beaker, o hot plate, o measuring cylinder o torsion balance


Weight clean dry 600 ml beaker = __________________

Add 500 ml of previously filtered water

Place beaker on a hot plate and evaporate the water slowly

When dry reweigh the beaker = ___________________

Change in mass is dissolved solid in 500 ml

Mass of dissolved solid in 1 L = __________________

Conclusion



Determination of the pH of water sample

Apparatus

o Water samples

o pH paper or pH meter

Procedure

o Dip a piece of pH paper into the water and compare with the appropriate colour chart

Or

o Calibrate the pH meter using a buffer solution

o Dip the pH electrode into the water sample

o Record the steady reading



To Determine the Hardness of a Sample of Water

Precautions

Wear safety glasses, use pipette filler, wear rubber gloves


o Burette, o 50 ml pipette, o Pipette filler, o Retort stand and clamp, o Conical flask, o White tile, o Buffer solution o 0.01M EDTA solution o Eriochrome black indicator

Procedure

o Collect sample of “hard water”

o Fill burette with 0.01 M EDTA

What does EDTA stand for? ____________________________________________________

o What type of container is it stored in? Why? _______________________________________

___________________________________________________________________________

o Pipette [using a pipette filler] 50 cm3 of hard water into a 150 cm3 conical flask

o Add 1 cm3 buffer solution

What does the buffer solution do? ______________________________________________

_________________________________________________________________________

o Add five drops of eriochrome black [front bench]

o Keep this as comparison because colour change is difficult to spot.

o Note the colour of the solution _________________________________________________

o Set up another conical flask as above

o Titrate using 0.01 M EDTA from burette


o Watch carefully for the colour change – it is hard to spot

o Do one rough and 2 accurate titres [ to within 0.1 ml]

Rough Accurate 1 Accurate 22nd reading/1st reading

Titre

Average Titre =

Calculate the number of milligrams of CaCO3 in 50 cm3

1 cm3 of 0.01 M EDTA ≡ 1 mg CaCO3

Titre ml of 0.01 M EDTA = _____ mg CaCO3

= _____ mg in 50 cm3 of water

= _____ * 20 mg in 1000 ml of water

p.p.m. = mg in a L

Conc. in p.p.m. =

Hardness of water =

Name the indicator used. ____________________________________________________________

What is the colour change of the indicator? _____________________________________________

If a sample of the water used in the experiment was boiled the average titre would be 3 cm3 less.

Calculate the hardness of the boiled sample.


Explain the difference in Hardness between the two samples.

Some Questions

What is hard water? _______________________________________________________________

Name the two types of hardness. ______________________________________________________

What substances cause each type of Hardness in water.

What is the opposite of hard water? ___________________________________________________

How can you recognise this type of water? _____________________________________________



To Determine the Dissolved Oxygen Concentration of a Water Sample

Precautions

Wear safety glasses, use pipette filler, wear rubber gloves

Apparatus

o 500 cm3 glass bottle, o Burette, o 50 cm3 pipette,o Pipette filler, o Retort stand and clamp, o Conical flask, o White tile, o Conc. alkaline Potassium iodide solution, o Conc. MnCl2 solution, o Conc. sulphuric acid, o Starch indicator, o 0.025 M sodium thiosulphate solution

Procedure

o Wet the bottle

Why? __________________________________________________________________

o Collect sample of water in bottle and stopper it underwater

Why stopper under water? __________________________________________________

________________________________________________________________________

o Add 1 cm3 of conc. alkaline Potassium iodide solution under the surface

o Add 1 cm3 of conc. manganese chloride solution under the surface

Why are concentrated solutions used? _________________________________________

________________________________________________________________________

o Note what happens when they are added ______________________________________

________________________________________________________________________

________________________________________________________________________


________________________________________________________________________

o Re-stopper bottle without trapping any air and mix well

o Add 5 cm3 of conc. sulphuric acid and mix till precipitate disappears.

o If it doesn’t dissolve add more conc. sulphuric acid till it does

o Fill burette with 0.025 M sodium thiosulphate solution

o Pipette [using a pipette filler] 100 cm3 of the solution into a 150 cm3 conical flask

o Titrate using 0.025 M sodium thiosulphate solution

o When the solution becomes straw coloured add a few drops of Starch Indictor

Why add the indicator at this point? ___________________________________________

________________________________________________________________________

________________________________________________________________________

o Note the colour of the solution and continue to add thiosulphate solution _____________

o Note the colour change _____________________________________________________

o Do one rough and 2 accurate titres [ to within 0.1 ml]

Rough Accurate 1 Accurate 22nd reading1st reading

Titre

Average Titre = 2.8 cm3

Calculations [from first principles]

2 Mn(OH)2 + O2 = 2 MnO(OH)2

MnO(OH)2(s) + 2 I-(aq) + 4 H+

(aq) = Mn2+(aq) + I2(aq) + 3 H2O(l)

I2(aq) + 2 S2O32-

(aq) = 2 I- (aq) + S4O62-

(aq)

Moles of thiosulphate = Volume * Molarity / 1000 = 2.8 * 0.025 /1000 = 0.00007

Moles of oxygen = ¼ moles of thiosulphate = ¼ * 0.00007 = 0.0000175

Mass of oxygen = 32 * moles = 32 * 0.0000175 = 0.00056

Mass of oxygen in 1 Litre = 1000 / volume¥ * mass of oxygen = 1000/50 * 0.00056 = 0.0112

Mass of oxygen in mg = 1000 * mass of oxygen in grams = 1000 * 0.0112 = 11.2


Dissolved oxygen level = 11.2 mg litre [ppm]

[volume¥ = volume in conical flask]

Alternative method of calculation

Let a be oxygen Va = 50 Ma = ? na = 1

Let b be thiosulphate Vb = 2.8 Mb = 0.025 nb = 4

Ma = VbMbna / nbVa = 2.8 * 0.025 * 1 / 4 * 50 = 0.00035

Convert to g/l = molarity * molar mass = 0.00035 * 32 = 0.0112

Convert to mg/l [ppm] = g/l * 1000 = 11.2 ppm

Some Questions

What would you have seen if there was no oxygen in the water? ___________________________

When did you add the indicator? _____________________________________________________

Why did you not add the indicator at the start of the titration? ______________________________

________________________________________________________________________________

________________________________________________________________________________

Name the indicator used. ___________________________________________________________

What is the colour change of the indicator? ____________________________________________

What does BOD stand for? _________________________________________________________

How is it measured? _______________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

What is it a measure of? ____________________________________________________________

Name a substance that has a high BOD. ________________________________________________

What is eutrophication? ____________________________________________________________

________________________________________________________________________________


What does it result in? _____________________________________________________________

________________________________________________________________________________


leaving certificate · web viewmany commercial bleaches are solutions of sodium hypochlorite...

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