JEE Chemistry 2025 Question with Solution

Given:

• Statement I: $\mathrm{CrO_3}$ is a stronger oxidizing agent than $\mathrm{MoO_3}$
• Statement II: $\mathrm{Cr(VI)}$ is more stable than $\mathrm{Mo(VI)}$

Find: Which statement is correct.

In the same group of transition metals, the oxidizing power of oxides in higher oxidation states generally decreases down the group, while the stability of higher oxidation states increases for the heavier elements.

For Statement I, chromium and molybdenum belong to Group 6. $\mathrm{CrO_3}$ contains chromium in the $+6$ oxidation state and $\mathrm{MoO_3}$ contains molybdenum in the $+6$ oxidation state. Because chromium is smaller and more electronegative, $\mathrm{Cr(VI)}$ is more readily reduced to lower oxidation states. Therefore, $\mathrm{CrO_3}$ acts as a stronger oxidizing agent than $\mathrm{MoO_3}$. So, Statement I is true.

For Statement II, the higher oxidation state becomes more stable down the group for heavier congeners such as molybdenum. Hence $\mathrm{Mo(VI)}$ is more stable than $\mathrm{Cr(VI)}$. So, Statement II is false.

Therefore, Statement I is true but Statement II is false. The correct option is B.

Given:

• $\mathrm{CrO_3}$ and $\mathrm{MoO_3}$ are oxides of Group $6$ elements in high oxidation state.
• We must test the truth of the two statements.

Find: The correct option based on oxidizing power and stability trends.

Statement I: $\mathrm{CrO_3}$ is a stronger oxidizing agent than $\mathrm{MoO_3}$.

Oxides of transition metals in very high oxidation states tend to show oxidizing character. As we move down the group from chromium to molybdenum, this oxidizing tendency decreases. Thus $\mathrm{CrO_3}$ is a stronger oxidizing agent than $\mathrm{MoO_3}$. Hence Statement I is true.

Statement II: $\mathrm{Cr(VI)}$ is more stable than $\mathrm{Mo(VI)}$.

This is incorrect because for heavier members of the group, higher oxidation states are comparatively more stable. Therefore $\mathrm{Mo(VI)}$ is more stable than $\mathrm{Cr(VI)}$. Hence Statement II is false.

So the correct conclusion is: Statement I is true but Statement II is false, which corresponds to option B.