Question

Which of the following oxidation reactions are carried out by both \( K_2Cr_2O_7 \) and \( KMnO_4 \) in acidic medium?
A. \( I^- \rightarrow I_2 \)
B. \( S^{2-} \rightarrow S \)
C. \( Fe^{2+} \rightarrow Fe^{3+} \)
D. \( I^- \rightarrow IO_3^- \)
E. \( S_2O_3^{2-} \rightarrow SO_4^{2-} \)
Choose the correct answer from the options given below:

• A. A, B and C Only
• B. A, D and E Only
• C. B, C and D Only
• D. C, D and E Only

Hint:

When dealing with strong oxidizers, always check which ions they can oxidize in acidic conditions.

Answer 1

The Correct Option is A

Let's analyze each oxidation reaction:

A. $I^- \rightarrow I_2$:
Both $K_2Cr_2O_7$ and $KMnO_4$ can oxidize iodide to iodine in acidic medium.
This reaction is possible with both oxidizing agents.

B. $S^{2-} \rightarrow S$:
Both $K_2Cr_2O_7$ and $KMnO_4$ can oxidize sulfide to sulfur in acidic medium.
This reaction is possible with both oxidizing agents.

C. $Fe^{2+} \rightarrow Fe^{3+}$:
Both $K_2Cr_2O_7$ and $KMnO_4$ can oxidize $Fe^{2+}$ to $Fe^{3+}$ in acidic medium.
This reaction is possible with both oxidizing agents.

D. $I^- \rightarrow IO_3^-$:
Both $K_2Cr_2O_7$ and $KMnO_4$ can oxidize iodide to iodate in acidic medium, but it requires a stronger oxidizing power.
This reaction is possible under strong conditions, but not always consistent in standard acidic conditions.

E. $S_2O_3^{2-} \rightarrow SO_4^{2-}$:
Thiosulfate oxidation to sulfate is more complex and specific to certain oxidizing power and conditions. $KMnO_4$ typically does not oxidize thiosulfate to sulfate quantitatively in acidic medium, while $K_2Cr_2O_7$ may do so under vigorous conditions.
This reaction is not consistently carried out by both oxidizing agents.

Therefore, reactions A, B, and C are the only ones that are consistently carried out by both $K_2Cr_2O_7$ and $KMnO_4$ under standard acidic conditions.

Final Answer:
The final answer is $ (3)\ A,\ B\ \text{and}\ C\ \text{only} $.