Hess’s law — Paper 1 · A Level Chemistry 9701

6 Given S(s) + O2(g) → SO2(g), ∆H o = –297 kJ mol –1 f and S(s) + 1 O2(g) → SO3(g) 1 ∆H o = –395 kJ mol –1 2 f what is the enthalpy change of reaction, ∆H o, of 2SO2(g) + O2(g) → 2SO3(g)? A –196 kJ mol –1 B –98 kJ mol –1 C +98 kJ mol –1 D +196 kJ mol –1

1 marks

Answer: A

This question in 9701/11 Oct/Nov 2005

9 Given CO(g) + 2 1 O2(g) → CO2(g) ∆Ho = –283 kJ mol–1 H2(g) + 2 1 O2(g) → H2O(l) ∆Ho = –286 kJ mol–1 H2O(g) → H2O(l) ∆Ho = –44 kJ mol–1 what is the change in enthalpy, ∆Ho, for the following reaction? CO2(g) + H2(g) → CO(g) + H2O(g) A –525 kJ mol–1 B –41 kJ mol–1 C +41 kJ mol–1 D +525 kJ mol–1

1 marks

Answer: C

This question in 9701/11 Oct/Nov 2006

10 Titanium occurs naturally as the mineral rutile, TiO2. One possible method of extraction of titanium is to reduce the rutile by heating with carbon. TiO2(s) + 2C(s) → Ti(s) + 2CO(g) The standard enthalpy changes of formation of TiO2(s) and CO(g) are –940 kJ mol–1 and –110 kJ mol–1 respectively. What is the standard enthalpy change of this reaction? A –830 kJ mol–1 B –720 kJ mol–1 C +720 kJ mol–1 D +830 kJ mol–1

1 marks

Answer: C

This question in 9701/11 May/June 2008

8 Red lead oxide, Pb3O4, is used in metal priming paints. It can be made by heating PbO in air. 6PbO(s) + O2(g) → 2Pb3O4(s) Which two values are needed to calculate the enthalpy change for this reaction? A enthalpy change of combustion of lead and enthalpy change of formation of Pb3O4 B enthalpy change of combustion of PbO and enthalpy change of formation of Pb3O4 C enthalpy change of formation of PbO and enthalpy change of atomisation of O2 D enthalpy change of formation of PbO and enthalpy change of formation of Pb3O4

1 marks

Answer: D

This question in 9701/11 Oct/Nov 2008

8 Hydrogen peroxide slowly decomposes into water and oxygen. The enthalpy change of reaction can be calculated using standard enthalpies of formation. (hydrogen peroxide(l)) = –187.8 kJ mol–1 (water(l)) = –285.8 kJ mol–1 Using a Hess cycle, what is the enthalpy change of reaction for this decomposition? 2H2O2(l) → 2H2O(l) + O2(g) A +98 kJ mol–1 B −98 kJ mol–1 C −196 kJ mol–1 D −947.2 kJ mol–1

1 marks

Answer: C

This question in 9701/11 May/June 2009

6 The first stage in the industrial production of nitric acid from ammonia can be represented by the following equation. 4NH3(g) + 5O2(g) 4NO(g) + 6H2O(g) Using the following standard enthalpy change of formation data, what is the value of the standard enthalpy change, ∆Ho, for this reaction? compound ∆Hf o / kJ mol–1 NH3(g) –46.1 NO(g) +90.3 H2O(g) –241.8 A +905.2 kJ mol–1 B –105.4 kJ mol–1 C –905.2 kJ mol–1 D –1274.0 kJ mol–1

1 marks

Answer: C

This question in 9701/11 Oct/Nov 2009

5 Given the following enthalpy changes, I2(g) + 3Cl2(g) → 2ICl3(s) ∆Ho = –214 kJ mol–1 I2(s) → I2(g) ∆Ho = +38 kJ mol–1 What is the standard enthalpy change of formation of iodine trichloride, ICl3(s)? A +176 kJ mol–1 B –88 kJ mol–1 C –176 kJ mol–1 D –214 kJ mol–1

1 marks

Answer: B

This question in 9701/11 May/June 2010

5 Given the following enthalpy changes, I2(g) + 3Cl2(g) → 2ICl3(s) ∆Ho = –214 kJ mol–1 I2(s) → I2(g) ∆Ho = +38 kJ mol–1 What is the standard enthalpy change of formation of iodine trichloride, ICl3(s)? A +176 kJ mol–1 B –88 kJ mol–1 C –176 kJ mol–1 D –214 kJ mol–1

1 marks

Answer: B

This question in 9701/12 May/June 2010

4 Given the following enthalpy changes, I2(g) + 3Cl2(g) → 2ICl3(s) ∆Ho = –214 kJ mol–1 I2(s) → I2(g) ∆Ho = +38 kJ mol–1 What is the standard enthalpy change of formation of iodine trichloride, ICl3(s)? A +176 kJ mol–1 B –88 kJ mol–1 C –176 kJ mol–1 D –214 kJ mol–1

1 marks

Answer: B

This question in 9701/13 May/June 2010

8 Enthalpy changes of combustion can be used to determine enthalpy changes of formation. The following equation represents the enthalpy change of formation of butane. 4C(s) + 5H2(g) → C4H10(g) By using the following standard enthalpy of combustion data, what is the value of the standard enthalpy change of formation, , for this reaction? compound o carbon –394 hydrogen –286 butane –2877 A –5883 kJ mol–1 B –129 kJ mol–1 C +129 kJ mol–1 D +2197 kJ mol–1

1 marks

Answer: B

This question in 9701/11 Oct/Nov 2010

11 Enthalpy changes of combustion can be used to determine enthalpy changes of formation. The following equation represents the enthalpy change of formation of butane. 4C(s) + 5H2(g) → C4H10(g) By using the following standard enthalpy of combustion data, what is the value of the standard enthalpy change of formation, , for this reaction? compound o carbon –394 hydrogen –286 butane –2877 A –5883 kJ mol–1 B –129 kJ mol–1 C +129 kJ mol–1 D +2197 kJ mol–1

1 marks

Answer: B

This question in 9701/13 Oct/Nov 2010

7 Titanium occurs naturally as the mineral rutile, TiO2. One possible method of extraction of titanium is to reduce the rutile by heating with carbon. TiO2(s) + 2C(s) → Ti(s) + 2CO(g) The standard enthalpy changes of formation of TiO2(s) and CO(g) are –940 kJ mol–1 and –110 kJ mol–1 respectively. What is the standard enthalpy change of this reaction? A –830 kJ mol–1 B –720 kJ mol–1 C +720 kJ mol–1 D +830 kJ mol–1

1 marks

Answer: C

This question in 9701/12 May/June 2011

7 Propanone has the molecular formula C3H6O. The enthalpy change of combustion of hydrogen is –286 kJ mol–1. The enthalpy change of combustion of carbon is –394 kJ mol–1. The enthalpy change of combustion of propanone is –1786 kJ mol–1. Using this information, what is the enthalpy change of formation of propanone? A –1106 kJ mol–1 B –540 kJ mol–1 C –254 kJ mol–1 D +1106 kJ mol–1

1 marks

Answer: C

This question in 9701/11 May/June 2012

12 Red lead oxide, Pb3O4, is used in metal priming paints. It can be made by heating PbO in air. 6PbO(s) + O2(g) → 2Pb3O4(s) Which two values are needed to calculate the enthalpy change for this reaction? A enthalpy change of atomisation of O2 and enthalpy change of formation of Pb3O4 B enthalpy change of formation of O2 and enthalpy change of formation of Pb3O4 C enthalpy change of formation of PbO and enthalpy change of atomisation of O2 D enthalpy change of formation of PbO and enthalpy change of formation of Pb3O4

1 marks

Answer: D

This question in 9701/12 May/June 2012

5 Propanone has the molecular formula C3H6O. The enthalpy change of combustion of hydrogen is –286 kJ mol–1. The enthalpy change of combustion of carbon is –394 kJ mol–1. The enthalpy change of combustion of propanone is –1786 kJ mol–1. Using this information, what is the enthalpy change of formation of propanone? A –1106 kJ mol–1 B –540 kJ mol–1 C –254 kJ mol–1 D +1106 kJ mol–1

1 marks

Answer: C

This question in 9701/13 May/June 2012

10 A student calculated the standard enthalpy change of formation of ethane, C2H6, using a method based on standard enthalpy changes of combustion. He used correct values for the standard enthalpy change of combustion of ethane (–1560 kJ mol–1) and hydrogen (–286 kJ mol–1) but he used an incorrect value for the standard enthalpy change of combustion of carbon. He then performed his calculation correctly. His final answer was –158 kJ mol–1. What did he use for the standard enthalpy change of combustion of carbon? A –1432 kJ mol–1 B –860 kJ mol–1 C –430 kJ mol–1 D –272 kJ mol–1

1 marks

Answer: C

This question in 9701/11 Oct/Nov 2012

10 A student calculated the standard enthalpy change of formation of ethane, C2H6, using a method based on standard enthalpy changes of combustion. He used correct values for the standard enthalpy change of combustion of ethane (–1560 kJ mol–1) and hydrogen (–286 kJ mol–1) but he used an incorrect value for the standard enthalpy change of combustion of carbon. He then performed his calculation correctly. His final answer was –158 kJ mol–1. What did he use for the standard enthalpy change of combustion of carbon? A –1432 kJ mol–1 B –860 kJ mol–1 C –430 kJ mol–1 D –272 kJ mol–1

1 marks

Answer: C

This question in 9701/12 Oct/Nov 2012

12 Propanone has molecular formula C3H6O. The enthalpy change of combustion of hydrogen is –286 kJ mol–1. The enthalpy change of combustion of carbon is –394 kJ mol–1. The enthalpy change of formation of propanone is –254 kJ mol–1. Using this information, what is the enthalpy change of combustion of propanone? A –2644 kJ mol–1 B –2294 kJ mol–1 C –1786 kJ mol–1 D –426 kJ mol–1

1 marks

Answer: C

This question in 9701/12 May/June 2013

3 Enthalpy changes that are difficult to measure directly can often be determined using Hess’ Law to construct an enthalpy cycle. Which enthalpy change is indicated by X in the enthalpy cycle shown? C(s) + 2H2(g) + 2O2(g) X CH4(g) + 2O2(g) CO2(g) + 2H2O(l) A – 4 × the enthalpy of combustion of hydrogen B + 4 × the enthalpy of combustion of hydrogen C – 2 × the enthalpy of formation of water D + 2 × the enthalpy of formation of water

1 marks

Answer: D

This question in 9701/11 May/June 2014

3 The enthalpy change of formation of carbon dioxide is –394 kJ mol–1. The enthalpy change of formation of water is –286 kJ mol–1. The enthalpy change of formation of methane is –74 kJ mol–1. What is the enthalpy change of combustion of methane? A –892 kJ mol–1 B –606 kJ mol–1 C +606 kJ mol–1 D +892 kJ mol–1

1 marks

Answer: A

This question in 9701/12 May/June 2014

11 The diagram shows the skeletal formula of cyclopropane. The enthalpy change of formation of cyclopropane is +53.3 kJ mol–1 and the enthalpy change of atomisation of graphite is +717 kJ mol–1. The bond enthalpy of H – H is 436 kJ mol–1 and of C – H is 410 kJ mol–1. What value for the average bond enthalpy of the C – C bond in cyclopropane can be calculated from this data? A 187 kJ mol–1 B 315 kJ mol–1 C 351 kJ mol–1 D 946 kJ mol–1

1 marks

Answer: B

This question in 9701/12 May/June 2014

9 The enthalpy change of formation of Mn(NO3)2(s) is –696 kJ mol–1. The enthalpy change of formation of MnO2(s) is –520 kJ mol–1. The enthalpy change of formation of NO2(g) is +33 kJ mol–1. On heating, Mn(NO3)2 decomposes into MnO2 and NO2. Mn(NO3)2(s) → MnO2(s) + 2NO2(g) What is the value of the standard enthalpy change of this reaction? A –242 kJ mol–1 B –209 kJ mol–1 C +209 kJ mol–1 D +242 kJ mol–1

1 marks

Answer: D

This question in 9701/13 May/June 2014

3 Ethanol is increasingly being used as a fuel for cars. The standard enthalpy change of formation of carbon dioxide is –393 kJ mol–1. The standard enthalpy change of formation of water is –286 kJ mol–1. The standard enthalpy change of formation of ethanol is –277 kJ mol–1. What is the standard enthalpy change of combustion of ethanol? A –1921 kJ mol–1 B –1367 kJ mol–1 C –956 kJ mol–1 D – 402 kJ mol–1

1 marks

Answer: B

This question in 9701/11 Oct/Nov 2014

3 Ethanol is increasingly being used as a fuel for cars. The standard enthalpy change of formation of carbon dioxide is –393 kJ mol–1. The standard enthalpy change of formation of water is –286 kJ mol–1. The standard enthalpy change of formation of ethanol is –277 kJ mol–1. What is the standard enthalpy change of combustion of ethanol? A –1921 kJ mol–1 B –1367 kJ mol–1 C –956 kJ mol–1 D – 402 kJ mol–1

1 marks

Answer: B

This question in 9701/12 Oct/Nov 2014

5 Hydrogen sulfide, H2S, is released from volcanoes. It reacts with oxygen in the air to form sulfur dioxide. 2H2S(g) + 3O2(g) → 2H2O(l) + 2SO2(g) ∆Hf o [H2S(g)] = –21 kJ mol–1 ∆Hf o [H2O(l)] = –286 kJ mol–1 ∆Hf o [SO2(g)] = –297 kJ mol–1 What is the standard enthalpy change of this reaction? A –1208 kJ mol–1 B –1124 kJ mol–1 C –562 kJ mol–1 D –541 kJ mol–1

1 marks

Answer: B

This question in 9701/13 Oct/Nov 2014

7 The standard enthalpy changes of combustion of glucose and ethanol are given as –2820 and –1368 kJ mol–1 respectively. Glucose, C6H12O6, can be converted into ethanol. C6H12O6(s) → 2C2H5OH(l) + 2CO2(g) What is the standard enthalpy change for this reaction? A –1452 kJ mol–1 B –84 kJ mol–1 C +84 kJ mol–1 D +1452 kJ mol–1

1 marks

Answer: B

This question in 9701/11 May/June 2015

32 The diagram illustrates the enthalpy changes of a set of reactions ΔH = –134 kJ mol–1 R S ΔH = +92 kJ mol–1 ΔH = –75 kJ mol–1 T U Which statements are correct? 1 The enthalpy change for the transformation U → R is + 42 kJ mol–1. 2 The enthalpy change for the transformation T → S is endothermic. 3 The enthalpy change for the transformation R → T is – 33 kJ mol–1.

1 marks

Answer: D

This question in 9701/12 Feb/March 2016

8 The equation for the complete combustion of propan-1-ol is shown. CH3CH2CH2OH(l) + 4 2 1 O2(g) → 3CO2(g) + 4H2O(l) Standard enthalpy changes of formation are given. compound CH3CH2CH2OH(l) CO2(g) H2O(l) ∆Hf o –303 kJ mol–1 –394 kJ mol–1 –286 kJ mol–1 What is the standard enthalpy change of combustion of propan-1-ol, in kJ mol–1? A –394 – 286 – 303 B 303 – (4 × 286) – (3 × 394) C 394 + 286 – 303 D (3 × 394) + (4 × 286) + 303

1 marks

Answer: B

This question in 9701/12 May/June 2016

6 The following data are needed for this question. (CO(g)) = –111 kJ mol–1 (CO2(g)) = –394 kJ mol–1 (Fe2O3(s)) = –822 kJ mol–1 Carbon monoxide reacts with iron(III) oxide. 3CO(g) + Fe2O3(s) → 3CO2(g) + 2Fe(s) What is the enthalpy change when 55.8 g of iron are produced by this reaction? A –27.0 kJ B –13.5 kJ C +13.5 kJ D +27.0 kJ

1 marks

Answer: B

This question in 9701/13 May/June 2017

8 Sulfur can be oxidised in two ways. S(s) + O2(g) → SO2(g) ∆H o = –296.5 kJ mol–1 2S(s) + 3O2(g) → 2SO3(g) ∆H o = –791.4 kJ mol–1 Sulfur trioxide can be made from sulfur dioxide and oxygen. 2SO2(g) + O2(g) → 2SO3(g) What is the standard enthalpy change for this reaction? A –1384.4 kJ mol–1 B –989.8 kJ mol–1 C –494.9 kJ mol–1 D –198.4 kJ mol–1

1 marks

Answer: D

This question in 9701/11 Oct/Nov 2017

7 The following data are needed for this question. (P4O10(s)) = –3012 kJ mol–1 (H2O(l)) = –286 kJ mol–1 (H3PO4(s)) = –1279 kJ mol–1 What is ∆H o for the reaction shown? P4O10(s) + 6H2O(l) → 4H3PO4(s) A –9844 kJ mol–1 B –388 kJ mol–1 C –97 kJ mol–1 D +2019 kJ mol–1

1 marks

Answer: B

This question in 9701/12 Oct/Nov 2017

8 Sulfur can be oxidised in two ways. S(s) + O2(g) → SO2(g) ∆H o = –296.5 kJ mol–1 2S(s) + 3O2(g) → 2SO3(g) ∆H o = –791.4 kJ mol–1 Sulfur trioxide can be made from sulfur dioxide and oxygen. 2SO2(g) + O2(g) → 2SO3(g) What is the standard enthalpy change for this reaction? A –1384.4 kJ mol–1 B –989.8 kJ mol–1 C –494.9 kJ mol–1 D –198.4 kJ mol–1

1 marks

Answer: D

This question in 9701/13 Oct/Nov 2017

9 Hess’ Law and bond energy data can be used to calculate the enthalpy change of a reaction. Bromoethane, CH3CH2Br, can be made by reacting ethene with hydrogen bromide. CH2=CH2 + HBr → CH3CH2Br What is the enthalpy change for this reaction? A – 674 kJ mol–1 B – 64 kJ mol–1 C +186 kJ mol–1 D +346 kJ mol–1

1 marks

Answer: B

This question in 9701/12 Feb/March 2018

7 Enthalpy changes of combustion can be used to determine enthalpy changes of formation. The following equation represents the enthalpy change of formation of butane. 4C(s) + 5H2(g) → C4H10(g) By using the following standard enthalpy of combustion data, what is the value of the standard enthalpy change of formation, , of butane? substance C(s) –394 H2(g) –286 C4H10(g) –2877 A –5883 kJ mol–1 B –129 kJ mol–1 C +129 kJ mol–1 D +2197 kJ mol–1

1 marks

Answer: B

This question in 9701/11 May/June 2018

33 Calcium reacts with water to form calcium hydroxide and hydrogen. Ca(s) + 2H2O(l) → Ca(OH)2(s) + H2(g) The standard enthalpy change for this reaction is – 414 kJ mol–1. What further information is needed in order to calculate the standard enthalpy change of formation of calcium hydroxide, Ca(OH)2(s)? 1 for H2O(l) 2 for H2(g) 3 first and second ionisation energies of Ca

1 marks

Answer: D

This question in 9701/11 May/June 2018

7 Anhydrous copper(II) chloride, CuCl 2, combines with water to form CuCl 2.2H2O. The standard enthalpy changes of formation for this reaction are shown in the table. H2O –286 CuCl 2 –206 CuCl 2.2H2O –808 What is the standard enthalpy change of the reaction shown? CuCl 2 + 2H2O → CuCl 2.2H2O A –1586 kJ mol–1 B –316 kJ mol–1 C –110 kJ mol–1 D –30 kJ mol–1

1 marks

Answer: D

This question in 9701/13 May/June 2018

7 Ethanol is increasingly being used as a fuel for cars. The standard enthalpy change of formation of carbon dioxide is –393 kJ mol–1. The standard enthalpy change of formation of water is –286 kJ mol–1. The standard enthalpy change of formation of ethanol is –277 kJ mol–1. What is the standard enthalpy change of combustion of ethanol? A –1921 kJ mol–1 B –1367 kJ mol–1 C –956 kJ mol–1 D – 402 kJ mol–1

1 marks

Answer: B

This question in 9701/12 Oct/Nov 2018

8 The standard enthalpy changes of combustion of carbon, hydrogen and methanol are shown. C(s) + O2(g) → CO2(g) = –394 kJ mol–1 H2(g) + 2 1 O2(g) → H2O(l) = –286 kJ mol–1 CH3OH(l) + 1 O2(g) → CO2(g) + 2H2O(l) 1 = –726 kJ mol–1 2 Which expression gives the standard enthalpy change of formation of methanol in kJ mol–1? A –394 + (–286) – (–726) B –394 + (–286 × 2) – 726 C –394 + (–286 × 2) – (–726) D –726 – (–394) – (–286 × 2)

1 marks

Answer: C

This question in 9701/12 Feb/March 2019

8 Two reactions and their enthalpy changes are shown. 2C(s) + 2H2(g) → C2H4(g) ∆H o = +52.2 kJ mol–1 C2H2(g) + H2(g) → C2H4(g) ∆H o = –175.8 kJ mol–1 These data can be used to calculate the enthalpy change for the reaction shown. 2C(s) + H2(g) → C2H2(g) ∆H o = X What is the value of X? A –228.0 kJ mol–1 B –123.6 kJ mol–1 C +123.6 kJ mol–1 D +228.0 kJ mol–1

1 marks

Answer: D

This question in 9701/11 May/June 2019

7 The following data are needed for this question. (N2H4(l)) = 50.6 kJ mol–1 (N2O4(g)) = 9.2 kJ mol–1 (H2O(g)) = –241.8 kJ mol–1 Hydrazine, N2H4(l), reacts with dinitrogen tetraoxide, N2O4(g), to form nitrogen gas and water vapour. 2N2H4(l) + N2O4(g) → 3N2(g) + 4H2O(g) What is the enthalpy change for this reaction? A –1077.6 kJ mol–1 B –856.8 kJ mol–1 C –301.6 kJ mol–1 D –182.0 kJ mol–1

1 marks

Answer: A

This question in 9701/13 Oct/Nov 2019

4 The following data are needed for this question. NaHCO3(s) + HCl (aq) → NaCl (aq) + H2O(l) + CO2(g) ∆H = –38.97 kJ mol–1 Na2CO3(s) + 2HCl (aq) → 2NaCl (aq) + H2O(l) + CO2(g) ∆H = –96.59 kJ mol–1 On heating, sodium hydrogencarbonate decomposes as shown. 2NaHCO3(s) → Na2CO3(s) + H2O(l) + CO2(g) What is the enthalpy change for this decomposition? A –57.62 kJ mol–1 B –18.65 kJ mol–1 C 18.65 kJ mol–1 D 57.62 kJ mol–1

1 marks

Answer: C

This question in 9701/12 Feb/March 2020

4 The enthalpy changes of two reactions are shown. K2CO3(s) + 2HCl (aq) → 2KCl (aq) + H2O(l) + CO2(g) ∆H = –34.0 kJ mol–1 KHCO3(s) + HCl (aq) → KCl (aq) + H2O(l) + CO2(g) ∆H = +32.8 kJ mol–1 What is the enthalpy change for the reaction shown? 2KHCO3(s) → K2CO3(s) + H2O(l) + CO2(g) A –31.6 kJ mol–1 B 1.2 kJ mol–1 C 66.8 kJ mol–1 D 99.6 kJ mol–1

1 marks

Answer: D

This question in 9701/13 May/June 2020

6 Which pair of standard enthalpy changes are numerically equal? A atomisation of CH4(g) and formation of CH4(g) B combustion of CH3OH(l) and combustion of graphite + 2(combustion of H2(g)) C combustion of graphite and formation of CO2(g) D neutralisation of HCl (aq) with NaOH(aq) and formation of H2O(l)

1 marks

Answer: C

This question in 9701/11 Oct/Nov 2020

33 The diagram illustrates the enthalpy changes of a set of reactions. ∆H = –134 kJ mol–1 R S ∆H = +92 kJ mol–1 ∆H = –75 kJ mol–1 T U Which statements are correct? 1 The enthalpy change for the transformation U → R is + 42 kJ mol–1. 2 The enthalpy change for the transformation T → S is endothermic. 3 The enthalpy change for the transformation R → T is – 33 kJ mol–1.

1 marks

Answer: D

This question in 9701/12 Oct/Nov 2020

6 Which pair of standard enthalpy changes are numerically equal? A atomisation of CH4(g) and formation of CH4(g) B combustion of CH3OH(l) and combustion of graphite + 2(combustion of H2(g)) C combustion of graphite and formation of CO2(g) D neutralisation of HCl (aq) with NaOH(aq) and formation of H2O(l)

1 marks

Answer: C

This question in 9701/13 Oct/Nov 2020

32 An energy cycle for the combustion of methane is shown. ∆H o CH4(g) CH4(g) + 2O2(g) c CO2(g) + 2H2O(l) ∆H o CH4(g) ∆H o f z C(s) + 2H2(g) + 2O2(g) Which expressions can be used to calculate the energy change, ? ∆H o z 1 ∆H o CH4(g) + ∆H o CH4(g) f c 2 ∆H o C(s) + 2∆H o H2(g) c c 3 ∆H o CO(g) + 2∆H o H2(g) c c

1 marks

Answer: B

This question in 9701/12 Feb/March 2021

4 is the standard enthalpy of formation of methane. is the standard enthalpy of combustion of carbon. is the standard enthalpy of combustion of hydrogen. CH4(g) + 2O2(g) CO2(g) + 2H2O(l) Which expression is equivalent to ? A – + B – 2 – C – + D + 2 –

1 marks

Answer: D

This question in 9701/11 May/June 2021

8 Which enthalpy change is indicated by X in the enthalpy cycle shown? C(s) + 2H2(g) + 2O2(g) CH4(g) CO2(g) + X CH4(g) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) A – 4  the enthalpy of combustion of hydrogen B + 4  the enthalpy of combustion of hydrogen C – 2  the enthalpy of formation of water D + 2  the enthalpy of formation of water

1 marks

Answer: D

This question in 9701/13 May/June 2021

9 The standard enthalpy of formation of NO2(g) is + 33.2 kJ mol–1. The standard enthalpy of formation of N2O4(g) is + 9.2 kJ mol–1. What is the standard enthalpy change for the reaction 2NO2(g)  N2O4(g)? A –57.2 kJ mol–1 B –24.0 kJ mol–1 C +42.4 kJ mol–1 D +75.6 kJ mol–1

1 marks

Answer: A

This question in 9701/12 May/June 2022

10 Magnesium carbonate decomposes when heated in a Bunsen burner flame. Values for the standard enthalpies of formation, , of the species involved are shown. MgCO3 = –1095.8 kJ mol–1 MgO = –601.7 kJ mol–1 CO2 = –393.5 kJ mol–1 What is the standard enthalpy change for the decomposition of magnesium carbonate? A +100.6 kJ mol–1 B +887.6 kJ mol–1 C +1095.8 kJ mol–1 D +2091 kJ mol–1

1 marks

Answer: A

This question in 9701/13 May/June 2022

9 The enthalpy changes of formation, , of both PCl 3 and PCl 5 are exothermic. PCl 3 reacts with chlorine. PCl 3(l) + Cl 2(g) → PCl 5(s) = –124 kJ mol–1 Which pair of statements is correct? statement 1 statement 2 A is less negative than The Cl 2 bond energy is needed in calculating (PCl 5). from enthalpies of formation. B is more negative than The Cl 2 bond energy is needed in calculating (PCl 5). from enthalpies of formation. C is less negative than The Cl 2 bond energy is not needed in calculating (PCl 5). from enthalpies of formation. D is more negative than The Cl 2 bond energy is not needed in calculating (PCl 5). from enthalpies of formation.

1 marks

Answer: C

This question in 9701/11 Oct/Nov 2022

9 The enthalpy changes of formation, , of both PCl 3 and PCl 5 are exothermic. PCl 3 reacts with chlorine. PCl 3(l) + Cl 2(g)  PCl 5(s) = –124 kJ mol–1 Which pair of statements is correct? statement 1 statement 2 A is less negative than The Cl 2 bond energy is needed in calculating (PCl 5). from enthalpies of formation. B is more negative than The Cl 2 bond energy is needed in calculating (PCl 5). from enthalpies of formation. C is less negative than The Cl 2 bond energy is not needed in calculating (PCl 5). from enthalpies of formation. D is more negative than The Cl 2 bond energy is not needed in calculating (PCl 5). from enthalpies of formation.

1 marks

Answer: C

This question in 9701/13 Oct/Nov 2022

11 Nitric acid is made industrially by the oxidation of ammonia. The overall equation for the process is shown. equation 1 NH3 + 2O2 →HNO3 + H2O The process happens in three stages. The equations and enthalpy changes for these stages are given. stage 1 4NH3 + 5O2 →4NO + 6H2O H = −904kJmol−1 stage 2 2NO + O2 →2NO2 H = −114kJmol−1 stage 3 4NO2 + O2 + 2H2O →4HNO3 H = −348kJmol−1 What is the enthalpy change of the process shown in equation 1? A −1480kJmol−1 B −370kJmol−1 C −341.5kJmol−1 D +82kJmol−1

1 marks

Answer: B

This question in 9701/12 Oct/Nov 2023

9 The enthalpy change for a reaction can be calculated from values of: ● enthalpies of formation, ● enthalpies of combustion, ● bond energies, E. The enthalpy change of the reaction given = . 2C2H6(g) + 3O2(g)  2CH4(g) + 2CO2(g) + 2H2O(l) Which expression could be used to calculate ? A (C2H6(g)) B 2 (C2H6(g)) – 2 (CH4(g)) C E(C–C) + 2E(C–H) – 4E(C=O) – 4E(H–O) D (CH4(g)) + (CO2(g)) + (H2O(l)) – (C2H6(g))

1 marks

Answer: B

This question in 9701/12 Feb/March 2024

9 An energy cycle is shown. CH4 + 2O2 X Y C + 2H2 + 2O2 CO2 + 2H2O Z The energy changes involved are X, Y and Z. The numerical value of energy change Y is either –890 or +890. The numerical value of energy change Z is either –964 or +964. Which of the three values are negative? A X and Z B X only C Y and Z D Y only

1 marks

Answer: C

This question in 9701/11 May/June 2024

9 The standard enthalpy change of combustion of carbon is –394 kJ mol–1. The standard enthalpy change of combustion of hydrogen is –286 kJ mol–1. The standard enthalpy change of formation of butane is –129 kJ mol–1. What is the standard enthalpy change of combustion of butane? A –551 kJ mol–1 B –2877 kJ mol–1 C –3135 kJ mol–1 D –4307 kJ mol–1

1 marks

Answer: B

This question in 9701/11 Oct/Nov 2024

10 Two standard enthalpy change of formation values are given. [VCl 2] = –452 kJ mol–1 [VCl 3] = –573 kJ mol–1 What is the enthalpy change for the reaction 3VCl 2  2VCl 3 + V ? A –210 kJ mol–1 B –121 kJ mol–1 C +121 kJ mol–1 D +210 kJ mol–1

1 marks

Answer: D

This question in 9701/12 Oct/Nov 2024

9 The standard enthalpy change of combustion of carbon is –394 kJ mol–1. The standard enthalpy change of combustion of hydrogen is –286 kJ mol–1. The standard enthalpy change of formation of butane is –129 kJ mol–1. What is the standard enthalpy change of combustion of butane? A –551 kJ mol–1 B –2877 kJ mol–1 C –3135 kJ mol–1 D –4307 kJ mol–1

1 marks

Answer: B

This question in 9701/13 Oct/Nov 2024

13 Carbon monoxide and methanol can react together to form ethanoic acid. CO(g) + CH3OH(l) CH3CO2H(l) Standard enthalpy changes of combustion are given in the table. standard enthalpy change compound of combustion, CO –283.0 kJ mol–1 CH3OH –726.0 kJ mol–1 CH3CO2H –874.1 kJ mol–1 What is the value for for the reaction between carbon monoxide and methanol? A –1883.1 kJ mol–1 B –134.9 kJ mol–1 C +134.9 kJ mol–1 D +1883.1 kJ mol–1

1 marks

Answer: B

This question in 9701/12 Feb/March 2025

6 Some standard enthalpy of combustion data are given. standard enthalpy change substance of combustion / kJ mol–1 C(s) –394 H2(g) –286 CH3OH(l) –726 Using these data, what is the enthalpy change of formation of methanol? A –240 kJ mol–1 B –46 kJ mol–1 C 46 kJ mol–1 D 240 kJ mol–1

1 marks

Answer: A

This question in 9701/12 May/June 2025

6 The first stage in the industrial production of nitric acid from ammonia can be represented by the following equation. 4NH3(g) + 5O2(g) 4NO(g) + 6H2O(g) Using the following standard enthalpy change of formation data, what is the value of the standard enthalpy change, Ho, for this reaction? compound NH3(g) –46.1 NO(g) +90.3 H2O(g) –241.8 A +905.2kJmol–1 B –105.4kJmol–1 C –905.2kJmol–1 D –1274.0kJmol–1

1 marks

Answer: C

This question in 9701/13 May/June 2025