13619.06R [Turn over 10 Calculate the standard enthalpy of formation of propane using the data below. C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(l) ∆HO —  =  -2220 kJ mol-1 H2(g) + 1 2 O2(g) → H2O(l) ∆HO —  =  -286 kJ mol-1 C(s) + O2(g) → CO2(g) ∆HO —  =  -394 kJ mol-1 A -1540 kJ mol-1 B -106 kJ mol-1 C +106 kJ mol-1 D +1540 kJ mol-1 Answer                         [1] 13619.06R Section B Answer all five questions in the spaces provided. 11 The Solvay process is used to produce sodium carbonate. The process consists of several steps involving the use of ammonia, sodium chloride and calcium carbonate. (a) The overall equation for the formation of sodium carbonate may be written as the reaction between calcium carbonate and sodium chloride. Write the overall equation for this process. [2] (b) The equation for one of the steps in the process is shown below. 2NH4Cl + Ca(OH)2 → CaCl2 + 2NH3 + 2H2O (i) Calculate the percentage atom economy for the formation of ammonia in the above reaction. Give your answer to 1 decimal place. Answer                         % [2] (ii) During this stage of the process, 3.25 tonnes of ammonium chloride are reacted with an excess of calcium hydroxide and 0.92 tonnes of ammonia were obtained. Calculate the percentage yield of ammonia. Give your answer to 1 decimal place. Answer                         % [3]