In the reaction E+F ↔ G+H; the backward reaction is favoured if the concentration of?

A. F is increased
B. E is increased
C. E is reduced
D. G is reduced

Correct Answer:

Option C – E is reduced

Explanation

Le chatalier’s principle states that whenever a change in temperature, pressure or concentration is imposed on a system in equilibrium, the equilibrium will shift so as to neutralise the change and restore equilibrium.

For a reaction in equilibrium, if you increase the concentration of one of the substances, the equilibrium will shift so as to reduce the concentration and restore equilibrium, conversely, if you reduce the concentration of one of the substances the equilibrium will shift to increase the concentration and restore equilibrium.

Option A :- F is increased
If F is increased, the equilibrium will shift so as to reduce the concentration of F, which means more of F will react with E to produce More of G and H, effectively reducing the concentration of G therefore the forward reaction is favoured

Option B:- E is increased
This is basically the same thing as the first one which means more of E will react with F to produce more of G and H, effectively reducing the concentration of E. So this also favours the forward reaction.

Option C:- E is reduced
If E is reduced, then the equilibrium will shift so as to increase the concentration of E, which means that more of G and H will react to form more of E and F, effectively increasing the concentration of E and favours the backward reaction.

Option D:- G is reduced
If G is reduced, then the equilibrium will shift so as to increase the concentration of G, this means that More of E and F will react to produce more of G and H will react to form more of E and F, effectively increasing the concentration of E and favours the backward reaction.

Option D:- G is reduced
If G is reduced, then the equilibrium will shift so as to increase the concentration of G, this means that More of E and F will react to produce more of G and H, which favours the forward reaction

So out of all the options, the only one that favours the reverse reaction is C