According to Le Chatelier's principle when a system at equilibrium is subjected to changes in temperature, pressure, volume then the equilibrium will shift in a direction to counteract the induced change.
The given equilibrium is:
N2O4(g) ↔ 2NO2(g)
Since Volume (V) is inversely related to the pressure (P), a decrease in V will cause an increase in P. Based on Le Chatelier's principle, the equilibrium will now shift to the direction of lower pressure i.e. towards the reactants (since the # moles of reactants is less than the products). As a result concentration of N2O4 will increase and that of NO2 will decrease.
Ans: B
NO2 less, N2O4 greater