JEE Main 2024 — Ionic Equilibrium Question with Solution

The equilibrium $${\mathrm{Cr}}_2{\mathrm{O}}_7^{2-}\rightleftharpoons 2{\mathrm{CrO}}_4^{2-}$$ can be influenced by changes in the pH of the medium, according to Le Chatelier's principle. This principle states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium moves to counteract the change.

In this case:

$${\mathrm{Cr}}_2{\mathrm{O}}_7^{2-}$$ is dichromate, which exists more prominently in acidic conditions. On the other hand, $${\mathrm{CrO}}_4^{2-}$$ is chromate, which is favored in basic conditions. When the medium is basic, hydrogen ion concentration decreases, leading to the formation of more chromate ions ($${\mathrm{CrO}}_4^{2-}$$).

Thus, in a basic medium, the reaction shifts to the right, resulting in the formation of $$2{\mathrm{CrO}}_4^{2-}$$ from $${\mathrm{Cr}}_2{\mathrm{O}}_7^{2-}$$.

Therefore, the correct option is:

Option B: a basic medium