Calcium carbonate thermally decomposes according to CaCO_3(s) CaO(s) + CO_2(g)

CHEMISTRY · Multi-part · A Level · Chemistry · Thermodynamics · Thermodynamics

Problem

Calcium carbonate thermally decomposes according to

\mathrm{CaCO_3(s)} \rightleftharpoons \mathrm{CaO(s)} + \mathrm{CO_2(g)}.

For this reaction, the standard enthalpy change is

\Delta H^\circ = +178\,\text{kJ mol}^{-1}

and the standard entropy change is

\Delta S^\circ = +160\,\text{J mol}^{-1}\,\text{K}^{-1}

. The gas constant is

R = 8.314\,\text{J mol}^{-1}\,\text{K}^{-1}

. (a) Calculate the standard Gibbs free-energy change

\Delta G^\circ

298\,\text{K}

. (b) Determine the equilibrium constant

K

298\,\text{K}

. (c) Repeat the calculations in parts (a) and (b) for

1200\,\text{K}

(assume

\Delta H^\circ

and

\Delta S^\circ

remain temperature-independent). Discuss how the change in temperature affects the magnitude of

K

and the position of equilibrium.