Two different gas-phase processes can be used to convert sulfur dioxide into sulfur…

CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)

Problem

Two different gas-phase processes can be used to convert sulfur dioxide into sulfur trioxide, an important intermediate in the production of sulfuric acid. Process A:

2\,SO_2(g) + O_2(g) \rightleftharpoons 2\,SO_3(g)

K_A = 9.2 \times 10^{3}

700\,\text{K}

Process B:

SO_2(g) + \frac{1}{2}\,O_2(g) \rightleftharpoons SO_3(g)

K_B = 95

700\,\text{K}

(operates in the presence of a different catalyst and reactor design) Assume ideal-gas behavior and identical reactant feed compositions (stoichiometric proportions) for both processes. Answer the following questions. (a) For each process, describe qualitatively the relative amounts of

SO_2

O_2

, and

SO_3

present at equilibrium. (b) Identify which process is expected to deliver the higher percent yield of

SO_3

under the stated conditions, and justify your answer using the given equilibrium constants. (c) Briefly explain why a manufacturer might still consider implementing the process with the lower equilibrium constant.

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