CIE Nov 2014 v1 Paper 2 Q2

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The Contact process for the manufacture of sulfuric acid was originally patented in the 19th century and is still in use today. PMT The key step in the overall process is the reversible conversion of sulfur dioxide to sulfur trioxide in the presence of a vanadium(V) oxide catalyst. 2SO2(g) + O2(g) 2SO3(g) H = 196 kJ mol1 (a) One way in which the sulfur dioxide for this reaction is produced is by heating the sul de ore iron pyrites, FeS2, in air. Iron(III) oxide is also produced. Write an equation for this reaction.[2] (b) The sulfur trioxide produced in the Contact process is reacted with 98% sulfuric acid. The resulting compound is then reacted with water to produce sulfuric acid. (i) Explain why the sulfur trioxide is notrst mixed directly with water.[1] (ii) Write equations for the two steps involved in the conversion of sulfur trioxide into sulfuric acid.[2] (c) (i) Sulfur dioxide and sulfur trioxide both contain only S=O double bonds. Draw labelled diagrams to show the shapes of these two molecules. SO2 SO3 (ii) For your diagrams in (i), name the shapes and suggest the bond angles. SO2 shapeSO3 shapeSO2 bond angleSO3 bond angle[2] [2]UCLES 2014 9701/21/O/N/14<br /> PMT (d) The conversion of sulfur dioxide into sulfur trioxide is carried out at a temperature of 400 C. (i) With reference to Le Chateliers Principle and reaction kinetics, state and explain one advantage and one disadvantage of using a higher temperature.[4] (ii) State the expression for the equilibrium constant, Kp, for the formation of sulfur trioxide from sulfur dioxide. Kp = (iii) 2.00 moles of sulfur dioxide and 2.00 moles of oxygen were put in aask and left to reach equilibrium. At equilibrium, the pressure in theask was 2.00105 Pa and the mixture contained 1.80 moles of sulfur trioxide. Calculate Kp. Include the units. [1] Kp =units =[5] [Total: 19]UCLES 2014 9701/21/O/N/14 [Turn over<br />

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