Chemical and Ionic Equilibrium 1 Question 33
34. When $\mathrm{NaNO}{3}$ is heated in a closed vessel, oxygen is liberated and $\mathrm{NaNO}{2}$ is left behind. At equilibrium,
(1986, 1M)
(a) addition of $\mathrm{NaNO}_{2}$ favours reverse reaction
(b) addition of $\mathrm{NaNO}_{3}$ favours forward reaction
(c) increasing temperature favours forward reaction
(d) increasing pressure favours reverse reaction
35 For the gas phase reaction,
$$ \mathrm{C}{2} \mathrm{H}{4}+\mathrm{H}{2} \rightleftharpoons \mathrm{C}{2} \mathrm{H}_{6} \quad(\Delta H=-32.7 \mathrm{kcal}) $$
carried out in a vessel, the equilibrium concentration of $\mathrm{C}{2} \mathrm{H}{4}$ can be increased by
$(1984,1 \mathrm{M})$
(a) increasing the temperature
(b) decreasing the pressure
(c) removing some $\mathrm{H}_{2}$
(d) adding some $\mathrm{C}{2} \mathrm{H}{6}$
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Solution:
- $\mathrm{NaNO}{3}(s) \rightleftharpoons \mathrm{NaNO}{2}(s)+\frac{1}{2} \mathrm{O}_{2}(g), \Delta H>0$
$\mathrm{NaNO}{3}$ and $\mathrm{NaNO}{2}$ are in solid state, changing their amount has no effect on equilibrium. Increasing temperature will favour forward reaction due to endothermic nature of reaction. Also, increasing pressure will favour backward reaction in which some $\mathrm{O}{2}(g)$ will combine with $\mathrm{NaNO}{2}(s)$ forming $\mathrm{NaNO}_{3}$.
