Question

Predict the shift in equilibrium when the volume is decreased on the equilibrium reaction: ${\mathrm{N}}_2\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\rightleftharpoons 2\mathrm{NO}\left(\mathrm{g}\right)$

Answer 1

• When there is a decrease in volume, the equilibrium will shift to favour the direction that produces fewer moles of gas.
• When there is an increase in volume, the equilibrium will shift to favour the direction that produces more moles of gas.
• In the reaction : ${\mathrm{N}}_2\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\rightleftharpoons 2\mathrm{NO}\left(\mathrm{g}\right)$

number of moles of reactants $\left({\mathrm{n}}_{\mathrm{R}}\right)$ = 2, number of moles of products $\left({\mathrm{n}}_{\mathrm{P}}\right)$ = 2

${\mathrm{n}}_{\mathrm{R}}={\mathrm{n}}_{\mathrm{P}}$

• The number of moles of products is equal to that of reactants, hence when the volume is decreased, there is no effect on the equilibrium.