At 900 K the following two equilibria and their equilibrium constants are known: • •…

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

Problem

At 900 K the following two equilibria and their equilibrium constants are known: •

\text{S}_2(g)+2\,\text{O}_2(g)\;\rightleftharpoons\;2\,\text{SO}_2(g)

K_{1}=4.2\times10^{23}

•

\text{SO}_2(g)+\tfrac12\,\text{O}_2(g)\;\rightleftharpoons\;\text{SO}_3(g)

K_{2}=8.3\times10^{2}

Using only these data, consider the overall process that converts elemental sulfur to sulfur trioxide:

\text{S}_2(g)+3\,\text{O}_2(g)\;\rightleftharpoons\;2\,\text{SO}_3(g)

(a) Construct, in symbolic form, an expression for the equilibrium constant

K_{\text{overall}}

of the target reaction in terms of

K_{1}

and

K_{2}

. Clearly indicate what mathematical operation is required for each constant. (b) Calculate the numerical value of

K_{\text{overall}}

at 900 K. (c) Based on your result, evaluate whether the formation of

\text{SO}_3(g)

from

\text{S}_2(g)

and

\text{O}_2(g)

is product‐favored or reactant‐favored under these conditions, and justify your conclusion with reference to the magnitude of

K_{\text{overall}}

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