JEE Chemistry 2025 Question with Solution

Given: Statements about the stability and redox behavior of $Al^{3+}$ and $Tl^{3+}$/$Tl^+$ are to be checked.

Find: Which set of statements is correct.

Using the inert pair effect, heavier Group $13$ elements like thallium show increased stability of the lower oxidation state, that is $+1$. Aluminum, being lighter, mainly shows the $+3$ oxidation state.

1. Statement (A): $Tl^{3+}$ is a powerful oxidising agent.

Since $Tl^{3+}$ readily gets reduced to the more stable $Tl^+$ state, it behaves as a strong oxidising agent. So, (A) is correct.

2. Statement (B): $Al^{3+}$ does not get reduced easily.

$Al^{3+}$ is a stable ion and is not easily reduced. So, (B) is correct.

3. Statement (C): Both $Al^{3+}$ and $Tl^{3+}$ are very stable in solution.

Although $Al^{3+}$ is stable, $Tl^{3+}$ is not very stable in solution and tends to reduce to $Tl^+$. So, (C) is incorrect.

4. Statement (D): $Tl^+$ is more stable than $Tl^{3+}$.

This follows directly from the inert pair effect. So, (D) is correct.

5. Statement (E): $Al^{3+}$ and $Tl^+$ are highly stable.

Both of these ions are stable oxidation states. So, (E) is correct.

Therefore, the correct statements are (A), (B), (D) and (E) only.

The correct option is B.

Given: A set of five statements involving oxidation states of aluminum and thallium.

Find: The combination of true statements.

The key idea is that thallium, being a heavier $p$-block element of Group $13$, shows the inert pair effect strongly, so its $+1$ oxidation state is more stable than its $+3$ oxidation state.

• $Tl^{3+}$ tends to gain electrons and convert to $Tl^+$, hence it acts as an oxidising agent.
• $Al^{3+}$ is the common and stable oxidation state of aluminum.
• Therefore, $Tl^{3+}$ is not very stable in solution, while $Tl^+$ is stable.

So the truth values are:

• (A) True
• (B) True
• (C) False
• (D) True
• (E) True

Hence, the correct set is (A), (B), (D) and (E) only, so the answer is B.