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CIE Jun 2014 v3 Paper 2 Q3
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![Nitrogen dioxide, NO2, can enter the atmosphere in a variety of ways. PMT (a) (i) State one natural and one man-made source of atmospheric NO2. naturalman-made[1] (ii) Write an equation to show how NO2 leads to the formation of nitric acid in acid rain.[1] (iii) Use equations to illustrate the catalytic role of NO2 in the formation of sulfuric acid in acid rain.[3] (b) Nitrogen dioxide exists in equilibrium with dinitrogen tetroxide, N2O4. 2NO2(g) N2O4(g) 2.00 mol of dinitrogen tetroxide was sealed in a container at 350 K. After equilibrium had been established the total pressure was 140 kPa and the mixture of gases contained 1.84 mol of dinitrogen tetroxide. (i) Give the expression for the equilibrium constant, Kp, for this equilibrium. Kp = (ii) Calculate the number of moles of NO2 present at equilibrium. [1] [1] (iii) Calculate the total number of moles of gas present at equilibrium and hence the mole fraction of each gas present at equilibrium.UCLES 2014 9701/23/M/J/14 [2]<br />
(iv) Calculate the partial pressure of each gas present at equilibrium. (v) Calculate the value of the equilibrium constant, Kp, at 350 K. Give your answer to three signi cantgures and include the units. PMT [2] Kp =units =[2] [Total: 13]UCLES 2014 9701/23/M/J/14 [Turn over<br />](https://learnah.org/wp-content/uploads/2018/08/June_2014_v3_QP_-_Paper_2_CIE_Chemistry_A-level_3-0.jpg)
![Page 4 Mark Scheme GCE AS LEVELMay/June 2014 Syllabus 9701 Paper 23 (a) (i) (reaction between atmospheric N2 and O2) due to lightning / biological processes or bacteria in soil AND in car engines / power stations / metal refining / furnaces (ii) 2NO2 + H2O HNO2 + HNO3 OR 2NO2 + H2O + 1 / 2O2 2HNO3 OR 3NO2 + H2O 2HNO3 + NO (iii) SO2 + NO2 SO3 + NO NO + 1 / 2O2 NO2 SO3 + H2O H2SO4 2 (b) (i) Kp = pN2O4 / (pNO2) (ii) moles of NO2 = 0.32 (iii) x(N2O4) = 1.84 / 2.16 = 0.85 x(NO2) = 0.32 / 2.16 = 0.15 ecf from (b)(ii) (iv) pN2O4 = 0.85140 = 119 (kPa) pNO2 = 0.15140 = 21 (kPa) ecf from (b)(iii) 2 (v) Kp = 119 / 21 = 0.270 kPa 1 ecf from (b)(i) and (b)(iv) (1) (1) (1) (1) (1) (1) (1) (1) (1) (1) (1) [1] [1] [3] [1] [1] [2] [2] (2) [2] Total 13Cambridge International Examinations 2014<br />](https://learnah.org/wp-content/uploads/2018/08/June_2014_v3_MS_-_Paper_2_CIE_Chemistry_A-level_3.jpg)