1 . ESTIMATION OF FERROUS ION BY CERIMETRY

Titration I: Standardisation of Cerium (IV) sulphate solution:

S. No.

Volume of Std FeSO4

(ml)

Burette reading (ml) Volume of CAS

(ml)Initial Final

Calculation :Volume of FeSO4 =

Normality of FeSO4 =

Volume of CAS =

Normality of CAS =--------------------N.

1. ESTIMATION OF FERROUS ION BY CERIMETRY

Exp. No: Date:

Aim:To estimate the amount of ferrous ion present in the whole of the given solution.A standard solution of

0.01N ferrous ammonium sulphate and an approximately 0.01N solution of Ceric ammonium sulphate are

supplied.

Principle:Ceric ions oxidise ferrous ions in acid medium according to the equation,

Ce+4+Fe+2→Ce3++Fe+ 3

The ceric ammonium sulphate solution of approximately known strength is standardized against

standard FAS.

For the above titrations, redox indicator ferroin can be used. Ferroin is a complex formed between

Fe(II) ion and 1,10-phenanthroline, [Fe(Phen)3]+2. The reduced form of indicator has an intense red colour,

whereas oxidised iron (III) complex has a blue colour. The indicator reaction may be written as,

[Fe (Phen )3 ]3++c [Fe (Phen )3 ]

+2

Pale blue Red

When iron (II) is titrated with Ce (IV) in sulphuric acid medium, the ferroin indicator is initially red in

colour in its reduced form.At the end point, Ce (IV) oxidises it to Fe (III) complex. The end point, is a sharp

change from red to pale blue colour.

Titration I: Standardisation of Cerium (IV) sulphate solution:Pipette out 20ml of Ferrous ammonium sulphate solution in to a clean conical flask. Add about 20ml of

2N sulphuric acid followed by 2 drops of ferroin indicator. Titrate it against Cerium (IV) solution taken in the

burette. The end point is colour change from red to pale blue colour. Repeat the titration to get concordant

value. From the titre value, calculate the strength of cerium (IV) solution.

Titration II: Estimation of Ferrous ionMake up the given ferrous ion solution to 100ml in a standard flask. Pipette out 20ml of this solution in to

a clean conical flask. Add about 20ml of 2N sulphuric acid solution and 2 drops of ferroin indicator. Titrate it

against standardised cerium (IV) solution taken in the burette. End point is colour change from red to pale blue

colour. Repeat the titration to get concordant value. From the titre value, calculate the strength of ferrous ion

and hence calculate the amount of ferrous ion present in the given solution.

Titration II: Estimation of Ferrous ion

S. No.

Volume of FeSO4

(ml)

Burette reading (ml) Volume of

CAS(ml)Initial Final

Calculation

Volume of CAS =

Normality of CAS =

Volume of FeSO4 =

Normality of FeSO4 = --------------------N.

The amount of Ferrous present in the whole of given solution =(Normality x Eq.Wt)/10

=----------------------g.

Result:The amount of ferrous ion present in the whole of the given solution = ___________g.

Experiment No.: 2 Date:…………

Objective: Determine the concentration of KMnO4 solution SpectrophotometricallyApparatus Required: UV- Visible spectrophotometer, cuvette, test tubes, pipette

Chemical required: KMnO4

Principle: When an electromagnetic radiation is passed through a sample, certain characteristic wavelengths are

absorbed by the sample as a result the intensity of the transmitted light is decreased. The measurement of the

decrease in intensity of the radiation is the basis of spectrophotometry.

The lmax of KMnO4 solution is calculated by plotting the graph in between the absorbance (A) and

wavelength and the concentration of the KMnO4 solution is calculated by plotting the graph in between the

absorbance (A) and concentration of the solution.

The relationship between absorbance and transmittance is illustrated in the following diagram:

Fig. 1

Significance:

UV / Visible spectrophotometers are used in the modern life science laboratory for the quantification of

nucleic acids, the determination of protein concentrations and the calculation of enzyme activity in kinetics

studies.

The purity of DNA and RNA extractions from cells can be readily measured using spectrophotometry

Procedure:

1. Switch ON the instrument and allow it to self calibrate.

2. Set the instrument as per the direction given by the instructor.

3. Prepare the solution of different concentrations from the given stock solution.

4. Note down the value of absorbance for different concentration of KMnO4 solution at 440 nm

wavelength (say 0.5%, 1.0%, 1.5%, 2.0% etc.)

5. Plot the observed values of absorbance against concentration.

6. Find the concentration of given unknown KMnO4 solution from the plotted graph.

Observation:

Determination of concentration of given KMnO4 solution

Sr. No. Concentration (C) Absorbance (A)

1.

2.

3.

4.

5.

6.

Unknown

Absorbance

Concentration

Graph in between absorbance and Concentration

Result:

Concentration of given KMnO4 = mg/l

Precautions:

1.Always use the dilute solution.

2. Cuvette should be cleaned properly and must be wiped with tissue paper.

3.Do not leave any finger marks on the cuvette.

Questions:

1. What is the purpose of this experiment? What is the relation between concentration and absorbance?

2. Mention the role of potassium permanganate in the water treatment.

3. What is the light source for visible region and UV region of the spectrum?

4. What are the advantages of using Quartz or silica cells over Glass and plastic when

measuring absorption of ultraviolet wavelengths by a solution?

5. Why is it important to determine lmax before determine the concentration of the

unknown?

3. ESTIMATION OF NICKEL IN AN ALLOY BY COMPLEXOMETRY

Exp. No: Date:

Aim:To estimate the amount of Nickel present in the whole of the given nickel alloy solution. A standard

solution of 0.01N Nickel sulphate and an approximately 0.01N EDTA solution are supplied.

Principle:

Nickel can be estimated by using EDTA as titrant and murexide as indicator. Murexide form complexes

with nickel at pH 11. Murexide is the ammonium salt of Purpuric acid. The colour change in the direct titration of

nickel at pH 10 – 11 is from yellow to bluish violet.

Procedure:Titration I: Standardisation of EDTA

Pipette out 20ml of standard nickel sulphate solution into a clean conical flask. Add a pinch of Murexide

indicator , and 10ml of 1M ammonium chloride solution and then add concentrated ammonia solution drop wise

till the pH is about 7 as shown by yellow colour of the solution. Titrate the mixture in conical flask against EDTA

taken in burette until colour changes from yellow to violet. (Nickel complexes rather slowly with EDTA and

consequently the EDTA solution must be added drop wise near the end point). Repeat the titration to get

concordant value. From the strength of Nickel sulphate solution calculate the strength of EDTA.

Titration II: Estimation of Nickel Transfer the given nickel alloy solution into a clean 100ml standard flask quantitaively and make upto

the mark using distilled water. Pipette out 20ml of made up nickel alloy solution into a clean conical flask. Add a

pinch of Murexide indicator and 10ml of 1M ammonium chloride solution and then add concentrated ammonia

solution drop wise till the pH is about 7 as shown by yellow colour of the solution. Titrate the mixture against

standardised EDTA taken in burette until colour changes from yellow to violet. Repeat the titration to get

concordant value. Calculate the strength of nickel solution by using strength of EDTA and hence the amount of

nickel present in the given solution.

Titration II: Estimation of Nickel

S. No. Volume of Nickel Sulphate

(ml)

Burette reading (ml) Volume of

EDTA(ml)Initial Final

Calculation

Volume of EDTA =

Normality of EDTA =

Volume of NiSO4 =

Normality of NiSO4 =--------------------N

The amount of Nickel present in the whole of given solution =(Normality x Eq.Wt)/10

=----------------------g.

Result:The amount of nickel present in the whole of the given solution = g.

Experiment No……4….. Date:…………….

Objective: To determine the concentration of iron in water sample by spectrophotometric method.

Requirements: Spectrophotometer. Stock solution of Fe3+ ions, conc. HCl, Potassium thiocyanate.

Principle: The colorimetric determination of iron using KCNS as colour developing agent is based on the

formation of a red coloured complex between Fe3+ and CNS- ions

Fe3+ + 3CNS ↔ [Fe (CNS)]2+

Red

Abs

Conc.

Absorbance of unknown solution

Concentration of unknown solution

In the determination of iron in the water sample, a series of standard solutions having iron is treated with KCNS

to get iron-thiocyanate complex. The absorbance of all the standard solution prepared is noted at λmax 480 nm

because iron-thiocyanate complex shows maximum absorbance at this wavelength. Now the absorbance for the

unknown solution is also determined. A graph is plotted against the absorbance (OD) against the concentrations

of the known solutions. From the graph the concentration of the unknown solution can be found out.

Procedure:

1. Set the Spectrophotometer and adjust the wavelength to 480 nm.

2. Prepare the stock solution of Fe3+ ions by dissolving 2.0g of ferric ammonium sulphate in 50 ml of

distilled water and 10 ml. of conc. HC1. HCl is added to suppress the hydrolysis of ferric ammonium

sulphate.

3. Take the stock solution in the burette and prepare 5 solutions of different known concentrations by

diluting the above stock solution in five different flasks.

4. Transfer 1 ml solution of standard stock solution to 50 ml measuring flask and add 10 ml of

thiocyanate solution. Dilute the solution to 50 ml.

5. Repeat the process (step 4) with the solutions of other concentrations prepared above and also with the

unknown sample.

6. Prepare the blank solution by dissolving 10 ml of thiocyanate solution in distilled water and making the

volume to 50 ml.

7. Keep the solution at rest for 5 minutes.

8. Note down the absorbance of all the solution against blank solution, spectrophotometrically at 480 nm.

9. Prepare a calibration curve by plotting absorbance against concentration.

10. From the calibration curve, the concentration of the unknown solution corresponding to its absorbance

can be found. 

Observation:

Observation:

S.No. Concentration Absorbance

Calibration Curve:

Result:

The amount of Fe(III) in water was found to be =………………g/L.

Questions:

1. What is spectrophotometry?

2. Discuss Lambert's and Beer's law of absorbance.

3. What is colorimetry?

4. What is absorbance, transmittanc/?, extinction coefficient.

5. How you can verify Beer's law?

6. How you can find out the conc. of the given unknown solution spectro. photometrically?

7. What is the significance of spectrophotometry.

8. What is the structure of orthophenanthroline complex with iron (II).

Experiment No. ……5….. Date:…………

Objective: To prepare Urea Formaldehyde resins.

Apparatus Required: Beaker, Measuring cylinder, Pipette, Glass rod, and Dropper

Chemicals required: (a) Urea Formaldehyde: Urea, Formaldehyde solution (40%), and Sulfuric acid (H2SO4)

Principle:

Polymers: The term polymer is derived from the Greek words ‘poly’ meaning many and ‘mer’ meaning part.

Thus, a polymer means a substance with many parts. Every polymeric substance has a definite identifying unit

of molecular structure, which is called a part or mer (monomer). A polymer is a large molecule made up of

small, simple chemical units held together by covalent bonds. Some polymers are linear in the form of chains

while others are branched or interlinked chains to form three-dimensional networks.

On the basis of reaction to stress and temperature polymers may be:

(i) Thermoplastics (Thermoplasts) which can be repeatedly given shapes by heat and pressure. Hence, once used

for a particular form, they can again be formed into a different shape or form, e.g. polyethylene (PE),

polystyrene (PS).

(ii) Thermosets are the polymers which once subjected to heat and pressure to give a particular form, cannot be

formed again like the thermoplastics, e.g. urea formaldehyde, phenol formaldehyde, nylon-6,6, etc.

(iii) Rubbers, when subjected to heat and pressure, behave at first like the thermoplastics and subsequently

become highly elastic. Their elasticity may be arrested at an intermediate stage and this process is called curing

(vulcanization)

On the basis of method of production, polymers are classified as:

(i) Addition (chain reaction) polymers are produced by addition or chain reaction polymerization in which a

simple, low molecular weight molecule (monomer), which possesses at least one double bond, is induced to

break its double bond resulting in the free valences, which then link up with other similar molecules to give the

polymer. In this polymerization, the monomer retains its identity in the polymer and also, no byproduct is

formed, e.g. polyethylene:

nCH2=CH2 CH2 CH2n

(ii) Condensation polymers are produced by the method of condensation polymerization in which the monomer

need not contain a double bond and the monomer does not retain its characteristic molecular formula in the

polymer. Moreover a small molecule is essentially given out and hence the resulting molecule is condensed in

the process, e.g.

Urea formaldehyde :

O H+ O

║ ║

H2N- C- NH2 + HCHO H2N- C-NH- CH2OH

Mono methylol urea

HCHO

O

║

HOH2C-HN- C-NH- CH2OH

Dimethylol urea

N-CH2-N-CH2-N-CH2

O=C O = C O = C

N-CH2-N-CH2-N-CH2

Cross Linked polymer

(Urea- Formaldehyde)

Procedure:

Take 1.5 gm of urea in a 100 ml beaker.

1. Add 3 ml of formaldehyde solution.

2. Stir the mixture till all the crystals of urea dissolve.

3. Now add 2 drops of Conc. H2SO4 when all of a sudden a white mass of urea formaldehyde resin

appears.

4. Wash the resin several times with tap water to remove any trace of acid.

5. Collect the white resin and take the weight.

Result:

The measured weight of the resin formed is ------------gm.

Precautions:

1. Be very careful while adding Sulphuric acid in the mixture.

2. Keep the beaker away from the body during the reaction.

3. Avoid inhaling the fumes coming out from the reaction mixture

Questions:1. What is polymer?

2. What arte natural polymer?

3. What are thermoplastic and thermoses polymers?

4. What is importance of Urea formaldehyde resin?

4. ESTIMATION OF ZINC USING POTASSIUM FERROCYANIDE BY PRECIPITATION

Titration I: Standardisation of Potassium ferrocyanide

S. No. Volume of Zinc Sulphate

(ml)

Burette reading (ml) Volume of Potassium

ferrocyanide

(ml)

Initial Final

Calculation:Volume of ZnSO4 =

Normality of ZnSO4 =

Volume of Potassium ferrocyanide =

Normality of Potassium ferrocyanide =--------------------N.

4. ESTIMATION OF ZINC USING POTASSIUM FERROCYANIDE BY PRECIPITATION METHOD

Exp. No: 6 Date:

Aim:

To estimate the amount of zinc present in the whole of the given solution using potassium ferrocyanide

by precipitation titration method. You are provided with a standard solution of 0.05 N zinc sulphate and an

approximately 0.05 N potassium ferrocyanide solution.

Principle: Zinc ions and ferrocyanide ions react in neutral or acid medium as follows

The zinc ions get precipitated as potassium zinc ferrocyanide.

The end point of the reaction can be detected using internal indicators such as diphenylamine, sodium

diphenylamine sulphonate etc. These substances are oxidation – reduction indicators (redox indicators) whose

action depends on the ratio of the concentration of ferricyanide in the solution. Thus in order to make the reaction

an redox reaction, a small quantity of potassium ferricyanide is added to the ferrocyanide solution. When an

excess of zinc ions are present in solution, the concentration of the ferrocyanide is very small and the reduction

potential is large. When all the zinc ions are quantitatively precipitated, the next drop of ferrocyanide that is

added in excess, will cause a sudden increase in [Fe(CN)6]2- and hence a sudden decrease in the potential. This

results in the colour change of the redox indicator. The end point is colour change from blue to yellowish green.

During titration, the solution should be thoroughly shaken, also the titration should be carried out very

slowly especially near the end point.

Procedure:Titration I: Standardisation of Potassium ferrocyanide

Exactly 20 ml of standard zinc sulphate solution is pipette out in to a clean conical flask. Add 20 ml of 4

N sulphuric acid, and 2 to 4 drops of diphenylamine indicator. Titrate this mixture against potassium ferrocyanide

taken in the burette. The end point is the colour change from blue to yellowish green. Repeat the titration for

concordant titre value. From the titre value calculate the strength of potassium ferrocyanide

Titration II: Estimation of Zinc

S. No.

Volume of Zinc Sulphate

(ml)

Burette reading (ml) Volume of Potassium

ferrocyanide

(ml)

Initial Final

Calculation Volume of Potassium ferrocyanide =

Normality of Potassium ferrocyanide =

Volume of ZnSO4 =

Normality of ZnSO4 =--------------------N.

The amount of Zinc present in the whole of given solution = (Normality x Eq.Wt)/10

=----------------------g.

Titration II: Estimation of Zinc Transfer the given Zinc alloy solution into a clean 100ml standard flask quantitatively and make upto

the mark using distilled water. Pipette out 20ml of made up solution in to a clean conical flask. Add 20ml of 4 N

sulphuric acid,and 2 to 4 drops of diphenylamine indicator. Titrate this mixture against potassium ferrocyanide

taken in the burette. The end point is the colour change from blue to yellowish green. Repeat the titration for

concordant titre value. From the titre value calculate the strength of zinc solution and from the strength estimate

the amount of zinc present in the whole of the given solution.

Result:The amount of Zinc present in the whole of the given solution = g.

Experiment No.: 7 Date:…………

Objective: Synthesis & Characterization of Silver Nanoparticles

Apparatus Required: UV- Visible spectrophotometer, cuvette, Beakers,Magnetic stirrer Chemical required: AgNO3, NaBH4 , PVA

Theory: The formation of silver nanoparticles can be observed by a change in color since small nanoparticles of silver are yellow. Sodium borohydride is used as a reducing agent and a layer of absorbed borohydride anions on the surface of the nanoparticles keep the nanoparticles separated. PVA acts as stabilizing agent. The scattering of light caused by spherically shaped colloidal silver nanoparticals shows golden yellow colour. When sodium cholride (NaCl) is added the nanoparticles aggregate and the suspension turns cloudy gray. The addition of a small amount of polyvinyl pyrrolidone will prevent aggregation.

Nanotechnology deals with processes that take place on the nanometer scale, that is, from approximately 1 to 100 nm. Properties of metal nanoparticles are different from those of bulk materials made from the same atoms. For example, silver metal is grayish,but colloidal silver from this synthesis is a clear yellow. The striking effect of nanoparticles on color has been known since antiquity when tiny metal particles were used to color glass in church windows. Silver particles stained the glass yellow, while gold particles were used to produce ruby glass.

Synthesis of Colloidal Ag

Colloidal silver is made by adding an excess of the reducing agent sodium borohydride, NaBH4 to silver nitrate, AgNO3. Particle size can also be determined using visible spectroscopy.

AgNO3 + NaBH4 Ag + 1/2H2 + 1/2B2H6 + NaNO3

Characterization of Colloidal Ag

Sample has to be characterized by UV spectroscopy. The presence of metal in the solution is related to a broad absorbance peak at 410 nm.The height of peak gives information about the metallic compound concentration in the medium. For the 12 nm Ag nanoparticles, the maximum wavelength is near 400 nm. In general, as the particles become larger the absorption maximum shifts to longer wavelengths.

When an electromagnetic radiation is passed through a sample, certain characteristic wavelengths are absorbed by the sample as a result the intensity of the transmitted light is decreased. The measurement of the decrease in intensity of the radiation is the basis of spectrophotometry.

The lmax of solution is calculated by plotting the graph in between the absorbance (A) and wavelength and the concentration of the solution is calculated by plotting the graph in between the absorbance (A) and concentration of the solution. Size and shape dependent colors of Au & Ag nanoparticles are shown in the table.

Procedure: 1.Take 1mL of 0.001M silver nitrate (AgNO3) and make it up to 10 mL.

2.Add 1mL of polyvinyl alcohol (PVA) 1% solution to the beaker slowly with constant stirring.3.Add a magnetic stir bar and place the flask on a stir plate and further add 40 mL of 0.0001M sodium borohydride (NaBH4) to above solution slowly with constant stirring.and and cool the liquid for about 20 minutes.4.Switch on the spectrophotometer and allow it to self calibrate.5.Take spectra to find a broad absorbance peak at 410 nm.

Result: Colour of silver nanoparticals:Shape of silver nanoparticals:Size of silver nanoparticals:

Precautions:1. Costant stirring should be done.2. Cuvette should be cleaned properly and must be wiped with tissue paper.3.Do not leave any finger marks on the cuvette.

Safety and Waste Disposal: Safety glasses are always required in the laboratory.Gloves must be worn throughout this experiment. Silver nitrate is caustic and stains theskin. A container will be made available for any waste solutions.

CAUTION: Stop the stirring as soon as the silver nitrate solution is added and remove the stir bar. If the stirring is continued once all the silver nitrate has been added,aggregation is likely to occur; the yellow darkens, turns violet, then grayish as the particles settle out.

The product should be clear yellow once the reaction is completed and should remainyellow, although it may darken somewhat. Record the appearance of your product assoon as the stirring is stopped and after waiting for about 5 minutes. If your product hasaggregated and turned gray---repeat the synthesis if possible.

Questions:1. What is the purpose of this experiment? What is the relation between concentration and absorbance? 2. Mention the colour, size and shape of nanoparticals of silver and gold.3. What are the main applications of silver and gold nanoparticals. 3. What is the light source for visible region and UV region of the spectrum?4. What are the advantages of using Quartz or silica cells over Glass and plastic when measuring absorption of ultraviolet wavelengths by a solution?5. Why is it important to determine lmax before determine the concentration of the unknown?