Chemistry Department

Chemistry Transition Task Yr11-12 2019

You are expected to complete these questions, bridging the gap between Yr11 and Yr12.

Please bring to your first Chemistry lesson.

There may be small areas of content that is not in GCSE, you are expected to use research skills to look up how to complete these questions.

Q1.A different kind of kiln is used to manufacture Portland cement. The main active minerals in Portland cement are called alite and belite.

(a)     The table shows the composition of a compound found in alite that contains only the elements calcium, silicon and oxygen. Use these percentage by mass data to determine

the empirical formula of this compound. 

Ca Si O

% by mass 52.67 12.30 To be calculated

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___________________________________________________________________(3)

(b)     A compound (Ca2SiO4) in belite reacts with water to produce Ca3Si2O4(OH)6 and Ca(OH)2

Write an equation for this reaction.

___________________________________________________________________(1)

(c)     Bags of Portland cement are labelled with hazard warnings.Suggest an item of personal safety equipment, other than eye protection, that the warning label recommends.Give a reason why this safety equipment is recommended.

Safety equipment __________________________________________________

Reason __________________________________________________________(2)

(Total 6 marks)

Q2.At room temperature, both sodium metal and sodium chloride are crystalline solids which contain ions.

(a)     On the diagrams for sodium metal and sodium chloride below, mark the charge for each ion.

 (2)

(b)     (i)      Explain how the ions are held together in solid sodium metal.

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(ii)     Explain how the ions are held together in solid sodium chloride.

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(iii)     The melting point of sodium chloride is much higher than that of sodium metal. What can be deduced from this information?

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(c)     Compare the electrical conductivity of solid sodium metal with that of solid sodium chloride. Explain your answer.

Comparison _________________________________________________________

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Explanation _________________________________________________________

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___________________________________________________________________(3)

(d)     Explain why sodium metal is malleable (can be hammered into shape).

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___________________________________________________________________(1)

(e)     Sodium chlorate(V), NaClO3, contains 21.6% by mass of sodium, 33.3% by mass of chlorine and 45.1% by mass of oxygen.

(i)      Use the above data to show that the empirical formula of sodium chlorate(V) is NaClO3

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(ii)     Sodium chlorate(V) may be prepared by passing chlorine into hot aqueous sodium hydroxide. Balance the equation for this reaction below.

....... Cl2 + ....... NaOH → ....... NaCl + NaClO3 + 3H2O(3)

(Total 12 marks)

Q3.In 2009 a new material called graphane was discovered. The diagram shows part of a model of the structure of graphane. Each carbon atom is bonded to three other carbon atoms and to one hydrogen atom.

 

(a)     Deduce the type of crystal structure shown by graphane.

___________________________________________________________________(1)

(b)     State how two carbon atoms form a carbon–carbon bond in graphane.

___________________________________________________________________(1)

(c)     Suggest why graphane does not conduct electricity.

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___________________________________________________________________(1)

(d)     Deduce the empirical formula of graphane.

___________________________________________________________________(1)

(Total 4 marks)

Q4.Central heating fuel, obtained by the fractional distillation of crude oil, contains saturated hydrocarbons with the molecular formula C16H34

(a)     Give the meaning of the terms saturated and hydrocarbon as applied to saturated hydrocarbons.

Saturated __________________________________________________________

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Hydrocarbon ________________________________________________________

___________________________________________________________________(2)

(b)     If the boiler for a central heating system is faulty, a poisonous gas may be produced during the combustion of C16H34

Write an equation for the reaction that forms this poisonous gas and one other product only.

___________________________________________________________________(1)

(c)     Explain why the sulfur compounds found in crude oil should be removed from the fractions before they are used for central heating fuel.

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___________________________________________________________________ (2)

(d)     A hydrocarbon C16H34 can be cracked to form C8H18, ethene and propene.

(i)      Write an equation to show this cracking reaction.

______________________________________________________________(1)

(ii)     Suggest one important substance manufactured on a large scale from propene.

______________________________________________________________(1)

(iii)    Draw the displayed formula of the functional group isomer of propene.

 

 

  

 (1)

(e)     There are many structural isomers with the molecular formula C8H18

Draw the structure of 2,3,3-trimethylpentane.

 

 

 

 (1)

(f)     A compound C8H18 reacts with chlorine to give several haloalkanes.

Give the IUPAC name of the following haloalkane.

 

___________________________________________________________________(1)

(Total 10 marks)

Q5. (a)     Crude oil is separated into fractions by fractional distillation. Outline how different fractions are obtained by this process.

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___________________________________________________________________(3)

(b)     The table below gives details of the supply of, and demand for, some crude oil fractions. 

FractionsApproximate %

Typical supply from crude oil

Globaldemand

Gases 2 4

Petrol and naphtha 16 27

Kerosine 13 8

Gas oil 19 23

Fuel oil and bitumen 50 38

(i)      Use the data given above to explain why catalytic cracking of crude oil fractions is commercially important.

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(ii)     Give the two main types of product obtained by catalytic cracking.

Type 1 ________________________________________________________

Type 2 ________________________________________________________(4)

(c)     Name a catalyst used in catalytic cracking. State the type of mechanism involved and outline the industrial conditions used in the process.

Catalyst ____________________________________________________________

Conditions __________________________________________________________(4)

(Total 11 marks)

Q6.(a)     Figure 1 shows the volume of hydrogen gas collected when a sample of magnesium

reacted with an excess of dilute hydrochloric acid.

The rate of this reaction can be studied by measuring the time it takes for a given volume of hydrogen to be collected.

Figure 1

 

Time / s

(i)      State the meaning of the term rate of reaction.

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______________________________________________________________(1)

(ii)     State and explain what has happened to the rate of this reaction at point W in Figure 1.

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(iii)     In terms of collision theory explain why, at a fixed temperature, the rate of this reaction doubles when the concentration of the hydrochloric acid doubles.

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(b)     In a study of the reaction in part (a), a student referred to activation energy.

(i)      State the meaning of the term activation energy.

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(ii)     Complete Figure 2 by drawing the shape of the reaction profile from reactants to products for an exothermic reaction.Show the position of the products. Show and label the activation energy.

Figure 2

 (2)

(c)     Barium metal reacts very quickly with dilute hydrochloric acid, but it reacts more slowly with water.

(i)      Write an equation for the reaction of barium with water.

______________________________________________________________(1)

(ii)     A solution containing barium ions can be used to show the presence of sulfate ions in an aqueous solution of sodium sulfate.

Write the simplest ionic equation for the reaction that occurs and state what is observed.

Simplest ionic equation

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Observation

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(iii)     State one use of barium sulfate in medicine.Explain why this use is possible, given that solutions containing barium ions are poisonous.

Use __________________________________________________________

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Explanation ____________________________________________________

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______________________________________________________________(2)

(Total 13 marks)

Q7.A student carried out a reaction between magnesium ribbon and aqueous trichloroethanoic acid in order to determine the enthalpy change. The equation for the reaction is shown:

Mg(s) + 2H+(aq) ⟶ Mg2+(aq) + H2(g)

The student measured the initial temperature of the trichloroethanoic acid and again every minute for 3 minutes before adding the magnesium ribbon at the fourth minute.The student continued to measure the temperature every minute for a further 10 minutes.The graph for these measurements is shown below.

 

The student used 240 mg of magnesium and 10.0 cm3 of aqueous trichloroethanoic acid (an excess).

Use these data and information determined from the graph above to calculate the enthalpy change, in kJ mol−1, for this reaction.Show your working.Give your answer to an appropriate precision.(The specific heat capacity of water = 4.18 J K−1 g−1)

Enthalpy change = ___________ kJ mol−1

(Total 7 marks)

Mark schemes

Q1.(a)     Percentage of oxygen 35.03     M1

Values used throughout must be to a minimum of 2 s.f.1

52.67 / 40.1     12.3 / 28.1     35.03 / 16     M2OR1.313     0.438     2.189

If ratios are inverted lose M2 and M31

Ca3SiO5     M3If correct formula only is given allow M3 only.

1

(b)     2 Ca2SiO4 + 4 H2O → Ca3Si2O4(OH)6 + Ca(OH)2

Accept multiples and fractions. Ignore state symbols.1

(c)     Gloves / Dust or face-maskIgnore references to use of fume cupboard.

1

Cement is alkaline / caustic / corrosive / irritantAccept ‘Ca(OH)2 formed is alkaline / caustic / corrosive / irritant’.

1[6]

Q2.(a)    

 [Diagrams must be complete and accurate]

2

(b)     (i)      Attraction /electrostatic forces/bonds/attractions between (positive)ions/lattice and delocalised/free electrons/sea of electrons.

[Not metallic bonding][Not just ‘forces’]

1

(ii)     Electrostatic attractions/forces between ions or attractionsbetween (oppositely charged) ions/ Na+ & Cl–

[Not ionic bonding]1

(iii)     (Here) the ionic bonding in NaCl is stronger/requires more energy tobreak than the metallic bonding in Na

QoL  Accept ‘bonding/forces of attraction in NaCl is stronger than in Na’[If IMF/molecules/van der Waals’/dipole–dipole mentionedin parts(i) or (ii), then CE = 0 for parts (i) and/or(ii) andCE = 0 for part(iii)]

1

(c)     Comparison:Sodium conducts and sodium chloride does NOT conduct

Allow ‘only Na conducts’Accept ‘Na conducts, NaCl only conducts when molten’[Do not accept sodium conducts better than sodium chloride etc.]

1

Explanation:(Delocalised) electrons flow though the metal

1

Allow e– move/carry current/are charge carriers/transfer charge.[Not ‘electrons carry electricity’][Not ‘NaCl has no free charged particles’]

Ions can’t move in solid salt1

(d)     Layers can slide over each other – idea that ions/atoms/particles move[Not molecules][Not layers separate]

1

(e)     (i)                    Na                     Cl                      O

                                    1

0.9(39)               0.9(38)               2.8(2)Hence:     1                        1                      3Accept backwards calculation, i.e. from formula to % composition,and also accept route via Mr to 23; 35.5; 48, and then to 1:1:3

[If % values incorrectly copied, allow M1 only][If any wrong Ar

values/atomic numbers used = CE = 0]1

(ii)     3Cl2 + 6NaOH → 5NaCl + NaClO3 + 3H2O1

[12]

Q3.(a)     Giant covalent / giant molecular / macromolecular

Not giant alone.

Not covalent alone.1

(b)      Shared pair of electrons / one electron from each C atom1

(c)      No delocalised / free / mobile electronsAllow all (outer) electrons involved in (covalent) bonds.Ignore ions.

1

(d)      CHAllow HCC and H must be capital letters.

1[4]

Q4.(a)     Saturated − single bonds only / no double bonds

1

Hydrocarbon − contains carbon and hydrogen (atoms) only1

(b)     C16H34 + 16.5O2 16CO + 17H2OAllow multiples

1

(c)     (On combustion) SO2 producedAllow equation to produce SO2. Ignore sulfur oxides.

1

Which causes acid rainIf formula shown it must be correctM2 is dependent on M1. But if M1 is sulfur oxides, allow M2.For M2 allow consequence of acid rain or SO2.

Ignore greenhouse effect and toxic1

(d)     (i)      C16H34 C8H18 + C2H4 + 2C3H6

Allow multiples1

(ii)     polypropene / propan(-1 or 2-)ol / propane(-1,2-)diol / isopropanol / propanone / propanal

Accept alternative namesIgnore plastic and polymer

1

(iii)    

 1

(e)     

 Allow any unambiguous representation

1

(f)     2,4-dichloro-2,4-dimethylhexaneOnly but ignore punctuation

1[10]

Q5.(a)     Crude oil is heated to vaporise it / oil vaporised (1)

(Vapour passed into fractionating) tower / column (1)Top of tower cooler than bottomor negative temperature gradient (1)fractions separated by b.pOR condensed at different temperatures OR levelsOR low boiling fractions at the topOR at the top small molecules or light components (1)

max 3

(b)     (i)      Identify shortfall in supply - e.g. petrol / small molecules (1)Higher value products OR more useful products (1)

OR cracking produces more of material (problem solving)

(ii)     Motor fuelsAromatic hydrocarbonsBranched alkanes / hydrocarbonsCycloalkanes

Any two (2)Ignore specific fractions, alkanes, shorter alkanes, penalise alkenes, and hydrogen

4

(c)     Catalyst: Zeolite / aluminosilicate (1)Type of mechanism: Carbocation / heterolytic fission (1)Conditions: High temp OR around 450 °C [300 – 600] °C NOT heat / warm (1)Slight pressure [> 1 atm  10 atm OR 1 megaPa, 1000 kPa] (1)

NOT high pressure4

[11]

Q6.(a)     (i)      Change in concentration (of a substance / reactant / product) in unit time /

given time / per (specified) unit of timeThis may be written mathematically OR may refer to the gradient of a graph of concentration / volume against time

OR

Amount of substance formed / used up in unit time / given time / per (specified) unit of time

Ignore additional information including reference to collisions1

(ii)     At W

M1 (QoL)

The rate / it is zero

M2

The magnesium has all reacted / has been used upIgnore reference to the acid being used up

OR

No more collisions possible between acid and Mg

OR

Reaction is complete / it has stopped

OR

No more hydrogen / product is produced2

(iii)    M1

Twice / double as many particles / hydrogen ions (in a given volume)Penalise reference to (hydrochloric acid) molecules in M1Penalise reference to “HCl particles” in M1

OR

Twice / double as much hydrochloric acid

M2

Twice / double as many effective / successful collisions (in a given time)

OR

Twice / double as many collisions with either sufficient energy to react OR with E ≥ Ea

OR

double the successful / effective collision frequency2

(b)    (i)      The activation energy is the minimum energy for a reaction to go / start

OR

Minimum energy for a successful/ effective collision1

(ii)     M1   Products lower than reactants on the profileMark independently

M2     Activation energy (Ea) shown and labelled correctly from reactants to peak of curveMark independently

2

(c)    (i)      Ba + 2H2O   Ba(OH)2 + H2

Ba + 2H2O  Ba2+ + 2OH− + H2

Allow multiplesIgnore state symbols

1

(ii)     M1    Ba2+ + SO42−  BaSO4

Ignore state symbols in M1Not multiples in M1

M2      White precipitate / solidExtra ions must be cancelledPenalise contradictory observations in M2

2

(iii)    M1     Barium meal / barium swallow / barium enemaAccept a correct reference to M1 written in the explanation in M2, unless contradictory

OR    used in X-rays OR to block X-rays OR X-ray contrast medium OR CT scans

M2      BaSO4 / barium sulfate is insoluble (and therefore not toxic)For M2 NOT barium ions      NOT barium      NOT barium meal and NOT “It”Ignore radio-tracing

2[13]

Q7.TWO correct extrapolations of best fit straight lines

Max 5/7 if no extrapolations or best fit straight linesdrawn

1

Use of their lines to calculate the temperature change at the 4th minute1

(17 °C)

Q = mcΔT

Q = 10 × 4.18 × [student’s temperature change]

Q = [710.6 J]Correct numbers inserted into expression.

1

Moles of Mg = 0.24 / 24.3 = 0.00988 mol1

ΔH = 710.6 / 0.00988 = 71923.07 J mol−1

1

ΔH = –72 (kJ mol−1)Must be negative to score M6

1

Answer to 2 significant figures1

[7]