Explain the effect of temperature change on chemical equilibrium with an example.

When a change in temperature of an equilibrium reaction occurs,the value of the equilibrium constant $K_{c}$ changes. In general,the temperature dependence of the equilibrium constant depends on the sign of $\Delta H$ for the reaction.
$1$. Exothermic reaction: The equilibrium constant for an exothermic reaction (negative $\Delta H$) decreases as the temperature increases. According to Le-Chatelier's principle,raising the temperature shifts the equilibrium to the left. For example,the production of ammonia is an exothermic reaction:
$N_{2(g)} + 3H_{2(g)} \rightleftharpoons 2NH_{3(g)} ; \Delta H = -92.38 \ kJ \ mol^{-1}$
Raising the temperature decreases the yield of ammonia. Thus,low temperature is favorable for a high yield,but a catalyst is used to maintain a practical reaction rate.
$2$. Endothermic reaction: The equilibrium constant for an endothermic reaction (positive $\Delta H$) increases as the temperature increases. The forward reaction is favored. For example:
$[Co(H_{2}O)_{6}]^{2+}_{(aq)} + 4Cl^{-}_{(aq)} \rightleftharpoons [CoCl_{4}]^{2-}_{(aq)} + 6H_{2}O_{(l)}$
(Pink) (Blue)
At room temperature,the mixture is blue. When cooled,the equilibrium shifts to the left,and the color turns pink due to the formation of $[Co(H_{2}O)_{6}]^{2+}$.