Question

Which of the following acts as a strong reducing agent? (Atomic number : Ce = 58, Eu = 63, Gd = 64, Lu = 71)

• A. $\text{Lu}^{3+}$
• B. $\text{Gd}^{3+}$
• C. $\text{Eu}^{2+}$
• D. $\text{Ce}^{4+}$

Answer 1

The Correct Option is C

To determine which ion acts as a strong reducing agent, we must understand the nature of reducing agents. A reducing agent donates electrons to other substances and gets oxidized in the process. The efficacy of a reducing agent depends on its tendency to lose electrons.

Let's analyze each given ion: 

• \(\text{Lu}^{3+}\): Lutetium typically exists in the +3 oxidation state, and it does not easily lose electrons to reach a lower oxidation state. Thus, it is not a strong reducing agent.
• \(\text{Gd}^{3+}\): Gadolinium also exists stably in the +3 oxidation state. Just like Lutetium, it is not prone to undergo reduction to a lower oxidation state, indicating that it is not a strong reducing agent.
• \(\text{Eu}^{2+}\): Europium's +2 oxidation state is less stable compared to its +3 state, making it more willing to donate electrons to achieve a stable +3 state. This tendency makes \(\text{Eu}^{2+}\) a strong reducing agent.
• \(\text{Ce}^{4+}\): Cerium in the +4 oxidation state is a strong oxidizing agent because it tends to accept electrons to revert to the more stable +3 state. Therefore, it acts as an oxidizing agent rather than a reducing agent.

From the above analysis, \(\text{Eu}^{2+}\) is identified as a strong reducing agent due to its tendency to lose an electron and achieve a stable +3 oxidation state.

Hence, the correct answer is \(\text{Eu}^{2+}\).

Answer 2

The strength of a reducing agent is determined by the ability of its ion to donate electrons. The element Eu (Europium) in its \( \text{Eu}^{2+} \) state can easily lose an electron to form \( \text{Eu}^{3+} \), making it a strong reducing agent. The reduction process is as follows:  
\(\text{Eu}^{2+} \rightarrow \text{Eu}^{3+} + e^-\)

This shows that \( \text{Eu}^{2+} \) acts as a strong reducing agent.  
Thus, the correct answer is 3, which corresponds to \( \text{Eu}^{2+} \).

The Correct Answer is: $\text{Eu}^{2+}$