JAMB Chemistry 2018 Paper

Concept:When the forward reaction is exothermic, heat acts like a product, and changing the temperature shifts the equilibrium.Explanation:The reaction is $\mathrm{2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g)}$, with $\Delta H = -395.7\,\mathrm{kJ\,mol^{-1}}$.A negative $\Delta H$ shows that the forward reaction releases heat.So an increase in temperature adds heat to the system.To reduce this extra heat, the equilibrium shifts in the direction that absorbs heat, which is the reverse reaction.Therefore, the equilibrium position shifts to the left, favouring the reactants.Also, for an exothermic reaction, increasing the temperature decreases the equilibrium constant, $K$.Hence, both effects match one option.Answer:A. left and equilibrium constant decreases