NEETChemistryd and f Block Elements
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): The standard reduction potential E ^ _ M ³⁺/ M ²⁺ for manganese is much more positive than that for iron. Reason (R): Mn ³⁺ ( d^4 ) is easily reduced to the highly stable d^5 configuration of Mn ²⁺ , whereas Fe ³⁺ already possesses a stable d^5 configuration and resists reduction to Fe ²⁺ ( d^6 ).
Options
- ABoth (A) and (R) are correct and (R) is the correct explanation of (A)
- BBoth (A) and (R) are correct but (R) is not the correct explanation of (A)
- C(A) is correct but (R) is not correct
- D(A) is not correct but (R) is correct
Correct answer
A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
Step-by-step solution
Assertion (A) is correct: The E ^ _ M ³⁺/ M ²⁺ value for Mn is highly positive ( +1.57 V ) compared to that of Fe ( +0.77 V ). Reason (R) is correct and explains (A): A highly positive E ^ value indicates a strong tendency to get reduced. Mn ³⁺ has a 3d^4 configuration and readily accepts an electron to form Mn ²⁺ , which has a highly stable exactly half-filled 3d^5 configuration. On the other hand, Fe ³⁺ already has a stable 3d^5 configuration, so its reduction to Fe ²⁺ ( 3d^6 ) is thermodynamically less favourabl