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KCET · Chemistry · d and f Block Elements

Which of the following will not act as an oxidising agent?

  1. A \(\text{CrO}_3\)
  2. B \(\text{MoO}_3\)
  3. C \(\text{CrO}_4^{2-}\)
  4. D \(\text{Cr}_2\text{O}_7^{2-}\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(\text{MoO}_3\)

Step-by-step Solution

Detailed explanation

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: \(\text{MoO}_3\)