The gas–phase rearrangement has a standard Gibbs free-energy change of

CHEMISTRY · Multi-part · AP · Chemistry · Thermodynamics and Electrochemistry · Thermodynamics and Electrochemistry

Problem

The gas–phase rearrangement

X \rightleftharpoons Y

has a standard Gibbs free-energy change of

\Delta G^{\circ}_{298}= -34.2\,\text{kJ\,mol}^{-1}

. At the same temperature, the forward elementary step is first order in X with

k_{\text{fwd}} = 1.0\times10^{-8}\,\text{s}^{-1}

. A rigid

1.00\,L

flask is charged with

1.00\,mol

of pure X at

298\,K

and

1.00\,bar

. (a) Calculate the equilibrium constant

K

for the reaction at

298\,K

. Report your answer to two significant figures. (b) Assuming the reverse rate is negligible during the first hour, estimate the fraction of X converted to Y after

1.0\,h

. Show all steps in your calculation. (c) Compare your answers from parts (a) and (b) to discuss whether the composition of the flask after

1.0\,h

is governed primarily by thermodynamic or kinetic factors. Justify your conclusion.

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