NEETChemistryd and f Block Elements
Which of the following sets of lanthanoid ions acts as good reducing agents in aqueous solutions?
Options
- ACe ⁴⁺ and Tb ⁴⁺
- BLa ³⁺ and Gd ³⁺
- CEu ²⁺ and Yb ²⁺
- DCe ⁴⁺ and Eu ²⁺
Correct answer
C. Eu ²⁺ and Yb ²⁺
Step-by-step solution
The most stable oxidation state for all lanthanoids is +3. Ions in the +2 oxidation state (such as Eu ²⁺ and Yb ²⁺ ) tend to lose one electron to achieve the more stable +3 state. Since they undergo oxidation, they act as good reducing agents. Conversely, ions in the +4 state (like Ce ⁴⁺ and Tb ⁴⁺ ) tend to gain an electron to reach the +3 state, acting as oxidising agents. Answer: Eu ²⁺ and Yb ²⁺