30 9 Ammonia is manufactured by the Haber Process. N2(g) + 3H2(g) ⇌ 2NH3(g) Kp = p p p ( ) ( ) ( ) NH N H 3 2 2 2 3 (a) The pressure used in the Haber Process is 200 atm. Explain the effect, if any, of increasing the pressure on the equilibrium yield of ammonia. (2) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (b) The equilibrium constants for Kp and Kc are related by the equation Kp = K RT c n ( )∆ where ∆n is the number of moles of reactants minus the number of moles of products. Calculate the value of Kc at 500 K when the value of Kp = 3.55 × 10−2 atm−2. Include the units for Kc . [Use the value of R = 0.0821 dm3 atm K−1 mol−1] (4) Turn over 31 (c) A mixture of 1.0 mol of nitrogen and 3.0 mol of hydrogen is left to reach equilibrium at 700 K. Calculate the total pressure, in atmospheres, needed to produce a yield of 0.30 mol of ammonia at 700 K. Give your answer to an appropriate number of significant figures. You must show your working. [Kp = 7.76 × 10−5 atm−2 at 700 K] (5) 32 (d) The value of the equilibrium constant, Kp , varies with temperature. The equation relating the values of the equilibrium constant at two temperatures is In K K 2 1 H R 1 1 T T 1 2 The equilibrium constant, K1 , for the formation of ammonia is 6.76 × 105 atm−2 when the temperature T1 = 298 K. The enthalpy change ∆H = −92 400 J mol−1. Calculate the value of the equilibrium constant for this reaction at 310 K. [Use the value of R = 8.31 J mol−1 K−1] (4) (Total for Question 9 = 15 marks) TOTAL FOR PAPER = 120 MARKS 33 BLANK PAGE 34 BLANK PAGE 35 BLANK PAGE 36