Phosgene, an important industrial intermediate, is formed by the equilibrium CO (g)+…

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

Problem

Phosgene, an important industrial intermediate, is formed by the equilibrium

\text{CO}(g)+\text{Cl}_2(g)\rightleftharpoons\text{COCl}_2(g)

The enthalpy change for the formation of one mole of phosgene is

\Delta H^{\circ}= -108\,\text{kJ}

. At

298\,\text{K}

the equilibrium constant is

K_c = 1.2\times10^{3}

. A sealed

2.00\,\text{L}

flask at equilibrium at

298\,\text{K}

is suddenly placed in a

350\,\text{K}

oven so that the temperature of the gas reaches

350\,\text{K}

almost instantaneously. No heat escapes and the volume of the flask remains fixed. The instantaneous concentrations immediately after the temperature jump (before any reaction can occur) are:

[\text{CO}] = 0.500\,\text{M}

[\text{Cl}_2] = 0.500\,\text{M}

[\text{COCl}_2] = 1.00\,\text{M}

. (a) Calculate the value of

K_c

for the reaction at

350\,\text{K}

. (b) Compute the reaction quotient

Q_c

for the mixture immediately after the temperature increase. (c) Predict the direction in which the system will proceed to reach equilibrium at

350\,\text{K}

and justify your prediction. (d) Determine the equilibrium concentrations of all species at

350\,\text{K}

. Show your reasoning clearly.

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