Two elementary equilibria involving sulfur oxides occur simultaneously at a fixed…

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

Problem

Two elementary equilibria involving sulfur oxides occur simultaneously at a fixed temperature. Reaction 1:

\mathrm{SO_2(g)}+\dfrac12\,\mathrm{O_2(g)}\;\rightleftharpoons\;\mathrm{SO_3(g)}

K_1 = 0.020

Reaction 2:

2\,\mathrm{SO_3(g)}\;\rightleftharpoons\;\mathrm{S_2O_6(g)}

K_2 = 5.0\times10^{3}

The overall reaction of interest is

2\,\mathrm{SO_2(g)}+\mathrm{O_2(g)}\;\rightleftharpoons\;\mathrm{S_2O_6(g)}

. Answer the following questions without performing a detailed numerical calculation. (a) Express the overall equilibrium constant

K_{\text{overall}}

symbolically in terms of

K_1

and

K_2

. (b) Determine whether

K_{\text{overall}}

is greater than 1, less than 1, or equal to 1. Explain your reasoning qualitatively, referencing the magnitudes of

K_1

and

K_2

. (c) Based on your answer to part (b), predict the sign of

\Delta G^{\circ}

for the overall reaction at this temperature and justify your prediction.

Related theory

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