Cambridge A Level Chemistry 9701 — 2011 May/June Paper 2 · Variant 1

This document consists of 11 printed pages and 1 blank page. DC (CW/DJ) 27048/3 © UCLES 2011 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level READ THESE INSTRUCTIONS FIRST Write your name, Centre number and candidate number on all the work you hand in. Write in dark blue or black pen. You may use a pencil for any diagrams, graphs, or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE ON ANY BARCODES. Answer all questions. You may lose marks if you do not show your working or if you do not use appropriate units. A Data Booklet is provided. The number of marks is given in brackets [ ] at the end of each question or part question. At the end of the examination, fasten all your work securely together. * 4 0 4 4 8 6 8 5 6 0 * CHEMISTRY 9701/21 Paper 2 Structured Questions AS Core May/June 2011 1 hour 15 minutes Candidates answer on the Question Paper. Additional Materials: Data Booklet For Examiner’s Use 1 2 3 4 5 Total

9701/21/M/J/11 © UCLES 2011 For Examiner’s Use Answer all the questions in the spaces provided. 1 Some intercontinental jet airliners use kerosene as fuel. The formula of kerosene may be taken as C14H30. (a) To which homologous series of compounds does kerosene belong? … [1] (b) When kerosene burns in an excess of air, carbon dioxide and water form. Balance the following equation for the complete combustion of kerosene. …C14H30(l) + …O2(g) …CO2(g) + …H2O(g) [1] (c) In this section, give your answers to one decimal place. The flight path from Beijing to Paris is approximately 8195 km. A typical intercontinental jet airliner burns 10.8 kg of kerosene for each kilometre covered. (i) Calculate the mass, in tonnes, of C14H30 burnt on a flight from Beijing to Paris. [1 tonne = 1 000 kg] (ii) Use your equation in (b) to calculate the mass, in tonnes, of CO2 produced during this flight. [4] 2

3 9701/21/M/J/11 © UCLES 2011 [Turn over For Examiner’s Use Bicycles may be carried on commercial airliners. When carried on airliners, bicycles are placed in the luggage hold. This is a part of the aircraft which, in flight, will have different temperatures and air pressures from those at sea level. This question concerns the change in pressure in an inflated bicycle tyre from when it is at sea level to when it is in the hold of an airliner in flight. (d) At sea level and a temperature of 20 °C an inflated bicycle tyre contains 710 cm3 of air at an internal pressure of 6 × 105 Pa. Use the general gas equation PV = nRT to calculate the amount, in moles, of air in the tyre at sea level. [2] The same bicycle, with its tyres inflated at sea level as described in (d) above, is placed in the luggage hold of an airliner. At a height of 10 000 m, the temperature in the luggage hold is 5 °C and the air pressure is 2.8 × 104 Pa. (e) Assuming the volume of the tyre does not change, use your answer to (d) to calculate the pressure inside the tyre at a height of 10 000 m. [2] [Total: 10]

4 9701/21/M/J/11 © UCLES 2011 For Examiner’s Use 2 Crude oil contains a mixture of hydrocarbons together with other organic compounds which may contain nitrogen, oxygen or sulfur in their molecules. At an oil refinery, after the fractional distillation of crude oil, a number of other processes may be used including ‘cracking’, ‘isomerisation’, and ‘reforming’. (a) (i) What is meant by the term ‘cracking ’ and why is it carried out? … … … … (ii) Outline briefly how the cracking of hydrocarbons would be carried out. … … (iii) Construct a balanced equation for the formation of heptane, C7H16, by cracking tetradecane, C14H30. … [4] One of the sulfur-containing compounds present in crude oil is ethanethiol, C2H5SH, the sulfur-containing equivalent of ethanol. Ethanethiol is toxic and is regarded as one of the smelliest compounds in existence. (b) The boiling point of ethanol, C2H5OH, is higher than that of C2H5SH. Suggest a reason for this difference. … …[1]

5 9701/21/M/J/11 © UCLES 2011 [Turn over For Examiner’s Use When ethanethiol is burned in an excess of air, three oxides of different elements are formed. (c) (i) Construct a balanced equation for this reaction. … (ii) Two of the oxides formed cause serious environmental damage. For each of these oxides, identify the type of pollution caused and describe one consequence of this pollution. … … … … … [6] (d) A small amount of ethanethiol is added to liquefied gases such as butane that are widely used in portable cooking stoves. Suggest a reason for this. …[1] Sulfur-containing compounds are removed from oil products at the refinery. The sulfur is recovered and converted into SO2, which is then used in the Contact process. (e) State the main operating details of the formation of SO3 in the Contact process. … … … … …[3] [Total: 15]

6 9701/21/M/J/11 © UCLES 2011 For Examiner’s Use 3 Calcium is the fifth most common element in the Earth’s crust. Calcium compounds occur in bones and teeth and also in many minerals. Some reactions of calcium and its compounds are shown in the reaction scheme below. U(aq) Ca(s) dilute HCl H2O(l) H2O(l) W(aq) reaction 1 X(s) V(s) roast in air dilute HNO3 dilute H2SO4 Z(s) Na2CO3(aq) Y(s) (a) State the formula of each of the calcium compounds U to Y. U … V … W … X … Y … [5] (b) Compound Y may be converted into compound V. Outline how this reaction would be carried out in a school or college laboratory using a small sample of Y. … …[1]

7 9701/21/M/J/11 © UCLES 2011 [Turn over For Examiner’s Use (c) (i) Construct balanced equations for the following reactions. calcium to compound U … compound V to compound W … compound U to compound Y … (ii) Construct a balanced equation for the effect of heat on solid compound W. … [4] (d) Suggest the formula of an aqueous reagent, other than an acid, for reaction 1. … [1] (e) What would be observed when each of the following reactions is carried out in a test- tube? the formation of X from Ca(s) … the formation of X from V … [2] [Total: 13]

8 9701/21/M/J/11 © UCLES 2011 For Examiner’s Use 4 Ketones are widely used as solvents and as intermediates in the chemical industry. Ketones contain the reactive keto group, C O. (a) Propanone, CH3COCH3, undergoes a reaction with hydrogen cyanide, HCN. (i) What type of reaction is this? … (ii) What reagents are used? … (iii) Draw a diagram to show the dipole present in the propanone molecule. [3]

9 9701/21/M/J/11 © UCLES 2011 [Turn over For Examiner’s Use (b) Propanone reacts with 2,4-dinitrophenylhydrazine reagent. H2N NO2 NO2 N H 2,4-dinitrophenylhydrazine (i) Construct a balanced equation for the reaction between propanone and 2,4-dinitrophenylhydrazine. (ii) A similar type of reaction occurs between propanone and hydroxylamine, NH2OH. Draw the displayed formula of the organic product of this reaction. H3C H3C C O + H H N OH [3] [Total: 6]

10 9701/21/M/J/11 © UCLES 2011 For Examiner’s Use 5 The gas ethyne, C2H2, more commonly known as acetylene, is manufactured for use in the synthesis of organic compounds. It is also used, in combination with oxygen, in ‘oxy-acetylene’ torches for the cutting and welding of metals. Industrially, ethyne is made from calcium carbide, CaC2, or by cracking liquid hydrocarbons. (a) When calcium carbide is reacted with water, ethyne and calcium hydroxide are formed. Construct a balanced equation for this reaction. …[1] Ethyne can also be obtained from ethene by using the following sequence of reactions. CH2CH2 HCCH ClCH2CH2Cl step 1 step 2 (b) (i) What types of reaction are step 1 and step 2? step 1 … step 2 … (ii) Suggest what reagent and conditions would be used in a laboratory in step 2. reagent … conditions … [5] When ethyne is passed into water at 60 °C, in the presence of a little H2SO4 and Hg2+ ions, a pungent, colourless organic liquid, Q, with Mr of 44 is obtained. This is step 3. When Q is warmed with Tollens’ reagent in a test-tube, a silver mirror is formed. On acidification, the solution remaining in the test-tube is found to contain the organic compound R which has Mr of 60. This is step 4. (c) (i) Give the structural formulae of Q and R. HCCH step 3 Q step 4 R (ii) What type of reaction is step 3 and step 4? step 3 … step 4 … [4]

11 9701/21/M/J/11 © UCLES 2011 For Examiner’s Use (d) The standard enthalpy change of combustion of C2H2, ΔH o–– c, is –1300 kJ mol–1 at 298 K. Values of relevant standard enthalpy changes of formation, ΔH o–– f, measured at 298 K, are given in the table. substance ΔH o–– f / kJ mol–1 CO2(g) –394 H2O(l) –286 (i) Write balanced equations, with state symbols, that represent the standard enthalpy change of combustion, ΔH o–– c, of C2H2, and … the standard enthalpy change of formation, ΔH o–– f, of C2H2. … (ii) Use the data above and your answer to (i) to calculate the standard enthalpy change of formation, ΔH o–– f, of C2H2. Show clearly whether the standard enthalpy change of formation of C2H2 has a positive or negative value. [6] [Total: 16]

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UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the May/June 2011 question paper for the guidance of teachers 9701 CHEMISTRY 9701/21 Paper 2 (AS Structured Questions), maximum raw mark 60 This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers. Mark schemes must be read in conjunction with the question papers and the report on the examination. • Cambridge will not enter into discussions or correspondence in connection with these mark schemes. Cambridge is publishing the mark schemes for the May/June 2011 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Page 2 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2011 9701 21 © University of Cambridge International Examinations 2011 1 (a) alkanes/paraffins not hydrocarbon (1) [1] (b) 2 C14H30 + 43 O2 → 28 CO2 + 30 H2O or C14H30 + 43/2O2 → 14 CO2 + 15 H2O (1) [1] (c) (i) mass of C14H30 burnt 8195 x 10.8 = 88.506 = 88.5 t (1) 1000 (ii) mass of CO2 produced Mr of C14H30 = (14 x 12 + 30 x 1) = 198 (1) 2 x 198 t of C14H30 → 28 x 44 t of CO2 88.5 t of C14H30 → 28 x 44 x 88.5 (1) 2 x 198 = 275.3 t of CO2 (1) allow 275.4 t if candidate has used 88.506 allow ecf on wrong value for Mr of C14H30 [4] (d) n = PV = 6 x 105 x 710 x 10-6 (1) RT 8.31 x 293 = 0.175 (1) [2] (e) P = nRT = 0.175 x 8.31 x 278 (1) V 710 x 10-6 = 569410.5634 Pa = 5.7 x 105 (1) allow ecf on (d) [2] [Total: 10]

Page 3 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2011 9701 21 © University of Cambridge International Examinations 2011 2 (a) (i) break large hydrocarbons into smaller hydrocarbons or break down large hydrocarbons (1) smaller hydrocarbons are more useful or smaller hydrocarbons are more in demand (1) (ii) using high temperatures/thermal cracking or using catalysts/catalytic cracking (1) (iii) C14H30 → C7H16 + C7H14 or C14H30 → C7H16 + C2H4 + C5H10 or C14H30 → C7H16 + C3H6 + C4H8 or C14H30 → C7H16 + 2C2H4 + C3H6 (1) do not allow any equation with H2 [4] (b) ethanol has hydrogen bonding, ethanethiol does not (1) [1] (c) (i) C2H5SH + 9/2 O2 → 2CO2 + SO2 + 3H2O or 2C2H5SH + 9O2 → 4CO2 + 2SO2 + 6H2O correct products (1) correct equation which is balanced (1) (ii) for CO2 enhanced greenhouse effect (1) global warming (1) for SO2 formation of acid rain (1) damage to stonework of buildings/ dissolving of aluminium ions into rivers/ damage to watercourses or forests/ aquatic life destroyed/ corrosion of metals (1) [6] (d) help detect leaks of gas (1) [1] (e) temperature of 450°C (1) pressure of 1 – 2 atm (1) V2O5/vanadium(V) oxide/vanadium pentoxide catalyst (1) [3] [Total: 15]

Page 4 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2011 9701 21 © University of Cambridge International Examinations 2011 3 dilute HCl roast in air H2O(l) H2O(l) dilute HNO3 Na2CO3(aq) dilute H2SO4 reaction 1 (a) U CaCl2 (1) V CaO (1) W Ca(NO3)2 (1) X Ca(OH)2 (1) Y CaCO3 (1) [5] (b) heat strongly in a test-tube or a boiling tube do not allow 'heat gently' or 'reflux' (1) [1] (c) (i) Ca to U Ca + 2HCl → CaCl2 + H2 (1) V to W CaO + 2HNO3 → Ca(NO3)2 + H2O (1) U to Y CaCl2 + Na2CO3 → CaCO3 + 2NaCl (1) (ii) 2Ca(NO3)2 → 2CaO + 4NO2 + O2 (1) [4] (d) Na2SO4(aq)/K2SO4(aq) or formula of any soluble sulfate (1) [1] U(aq) CaCl2 Ca(s) V (s) CaO Y(s) CaCO3 X(s) Ca(OH)2 Z(s) CaSO4 W(aq) Ca(NO3)2

Page 5 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2011 9701 21 © University of Cambridge International Examinations 2011 (e) (i) Ca to X colourless gas formed/fizzing/effervescence/bubbles or Ca dissolves or white precipitate/suspension formed (1) (ii) strongly exothermic/vigorous reaction or steam formed/steamy fumes or surface crumbles (1) do not allow white ppt. [2] [Total: 13] 4 (a) (i) nucleophilic addition (1) both words are necessary (ii) NaCN and H2SO4 or HCN plus CN– do not allow HCN on its own (1) (iii) correct δ+ and δ-, i.e. C Oδ− δ+ (1) [3] (b) (i) correct organic product (CH3)2C N NH NO2 NO2 C=N bond must be clearly shown (1) H2O formed/ equation balanced (1) [2] (ii) N O H C H3C H3C (1) [1] [Total: 6]

Page 6 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2011 9701 21 © University of Cambridge International Examinations 2011 5 (a) CaC2 + 2H2O → Ca(OH)2 + C2H2 (1) [1] (b) (i) step 1 electrophilic (1) addition (1) step 2 elimination or dehydrohalogenation (1) (ii) reagent NaOH/KOH/OH– (1) conditions in alcohol/ethanol (1) only allow conditions mark if reagent is correct [5] (c) (i) Q is CH3CHO ( as minimum) (1) R is CH3CO2H (as minimum) (1) (ii) step 3 is addition (1) step 4 is oxidation/redox (1) [4] (d) (i) combustion C2H2(g) + 5/2O2(g) → 2CO2(g) + H2O(l) or equation must be for the combustion of one mole of C2H2 H2O must be shown as liquid (1) correct state symbols in this equation (1) formation 2C(s) + H2(g) → C2H2(g) no mark for state symbols here (1) (ii) let Z be ∆Ho f of C2H2 C2H2 + 5/2O2 → 2CO2 + H2O ∆Ho f Z 0 2(-394) -286 ∆Ho c = -1300 = 2(-394) + (-286) – Z (1) whence Z = 2(-394) + (-286) – (-1300) = +226 kJ mol-1 value (1) sign (1) allow ecf on wrong equation [6] [Total: 16]