Q97 / 240 · KCET 2026 · Chemistry
Which of the following will not act as an oxidising agent?
- A$\text{CrO}_3$
- Correct answerB$\text{MoO}_3$
- C$\text{CrO}_4^{2-}$
- D$\text{Cr}_2\text{O}_7^{2-}$
Solution
In Group 6 elements (Cr, Mo, W), the stability of the higher oxidation state (+6) increases down the group.
Therefore, Mo(VI) and W(VI) are much more stable than Cr(VI).
Compounds of Cr(VI) such as $\text{CrO}_3$, $\text{CrO}_4^{2-}$, and $\text{Cr}_2\text{O}_7^{2-}$ are strong oxidising agents because Cr(VI) can easily be reduced to the more stable Cr(III) state.
On the other hand, Mo(VI) in $\text{MoO}_3$ is highly stable and does not undergo reduction easily. Thus, $\text{MoO}_3$ does not act as an oxidising agent.
Answer: $\text{MoO}_3$
Therefore, Mo(VI) and W(VI) are much more stable than Cr(VI).
Compounds of Cr(VI) such as $\text{CrO}_3$, $\text{CrO}_4^{2-}$, and $\text{Cr}_2\text{O}_7^{2-}$ are strong oxidising agents because Cr(VI) can easily be reduced to the more stable Cr(III) state.
On the other hand, Mo(VI) in $\text{MoO}_3$ is highly stable and does not undergo reduction easily. Thus, $\text{MoO}_3$ does not act as an oxidising agent.
Answer: $\text{MoO}_3$
Hence, the correct answer is option: 'B'.