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CIE Nov 2015 v1 Paper 2 Q2
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![(a) (i) Explain the meaning of the term enthalpy change of formation. PMT[2] (ii) Give the equation for the reaction for which the enthalpy change corresponds to the standard enthalpy change of formation of liquid sulfur trioxide, SO3. Include state symbols.[1] (b) Ammonia is manufactured by the Haber process. N2(g) + 3H2(g) 2NH3(g) (i) Use bond energies from the Data Booklet to calculate the enthalpy change of reaction for the Haber process. Include a sign in your answer. enthalpy changekJ mol1 [3] (ii) State the essential operating conditions for the Haber process.[3] (iii) Explain the choices of temperature and pressure for the Haber process.[4]UCLES 2015 9701/21/O/N/15<br />
PMT (c) One of the major uses of ammonia is in the manufacture of fertilisers such as diammonium hydrogen phosphate, (NH4)2HPO4. (i) Write an equation for the formation of diammonium hydrogen phosphate by the reaction between ammonia and phosphoric acid, H3PO4.[1] (ii) Explain this reaction in terms of the Brnsted-Lowry theory.[2] (d) The use of nitrate fertilisers can give rise to environmental consequences in terms of effects on both rivers and the atmosphere. (i) Explain how the uncontrolled use of nitrate fertilisers can result in a severe reduction in water quality in rivers.[3] (ii) Oxides of nitrogen are produced by the action of bacteria on nitrate fertilisers. Explain the problems associated with the release of oxides of nitrogen into the atmosphere. Include an equation in your answer.[2] [Total: 21]UCLES 2015 9701/21/O/N/15 [Turn over<br />](https://learnah.org/wp-content/uploads/2018/08/November_2015_v1_QP_-_Paper_2_CIE_Chemistry_A-level_2-0.jpg)
![Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A LevelOctober/November 2015 9701 21 PMT Question Mark Scheme (iii) pV RT OR pV = nRT (iv) Al2Cl mRT 1.36 8.31 473 M = pV 100 10 200 10 = 267 pV n = RT 1001020010 6 8.31473 5.09 = 10 1.36 5.09 10 267 (a) (i) The enthalpy change when one mole of a compound is formed from its element(s) (ii) S(s) + 1O2(g)SO3(l) (b) (i) 944 + (3436) = 2252 6390 = 2340 22522340 = 88 (kJ mol (ii) Fe catalyst 200 atm 400500 ()C (iii) High T increases rate AND Low T improves yield owtte Chosen temp is a compromise High P favours / increases (both rate and) yield owtte pressure chosen limited by cost (of compression and thick walls)Cambridge International Examinations 2015 Mark Total [1] [1] [1] [1] [2] [1] [1] [13] [1] [1] [2] [1] [1] [1] [1] [1] [1] [1] [1] [1] [1] [1] [1] [3] [3] [4]<br />
Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A LevelOctober/November 2015 9701 21 Question Mark Scheme (c) (i) 2NH3 + H3PO4(NH4)2HPO4 (ii) NH3 identified as base AND H3PO4 identified as acid base accepts protons AND acid donates protons (d) (i) nitrates / fertilisers wash into rivers eutrophication / algal bloom / promote algal growth bacteria use up oxygen in decay process (ii) (oxides of nitrogen / NOx / NOs) cause acid rain 2NO2 + H2OHNO2 + HNO3 OR 4NO2 + 2H2O + O24HNO3 OR SO2 + NO2SO3 + NO AND SO3 + H2OH2SO4 PMT Mark Total [1] [1] [1] [1] [1] [1] [1] [1] [1] [2] [3] [2] [21] (a) (i) structural isomers: (different molecules with) same molecular formula but different structural formulae chiral: has a carbon / C attached to 4 different groups / atoms / chains OR has no plane / line of symmetry / has non-superimposable mirror images (ii) CH3CH2CH(CH3)CH2CH2CH3 3-methylhexane CH3CH(CH3)CH(CH3)CH2CH3 2,3-dimethylpentane / (CH3)2CHCH(CH3)CH2CH3 (b) (i) C7H16 + 11O27CO2 + 8H2O (ii) C7H16 + 4O27C + 8H2OCambridge International Examinations 2015 [1] [1] [1] [1] [1] [1] [2] [4] [1] [1] [1] [1]<br />](https://learnah.org/wp-content/uploads/2018/08/November_2015_v1_MS_-_Paper_2_CIE_Chemistry_A-level_2-0.jpg)
