JEE MainChemistryd 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 electrode potential E^ ( M ³⁺/ M ²⁺) for manganese is highly positive compared to that of iron. Reason R: The third ionisation enthalpy of manganese is exceptionally high because removing an electron disrupts the stable half-filled 3 d ^5 configuration of Mn ²⁺ . In the light of the above st
Options
- ABoth A and R are true but R is NOT the correct explanation of A
- BA is true but R is false
- CA is false but R is true
- DBoth A and R are true and R is the correct explanation of A
Correct answer
D. Both A and R are true and R is the correct explanation of A
Step-by-step solution
Assertion A is true. The standard electrode potential E^ ( Mn ³⁺/ Mn ²⁺) is +1.57 ~V , which is highly positive compared to E^ ( Fe ³⁺/ Fe ²⁺) which is +0.77 ~V . Reason R is also true and provides the correct explanation. The value of E^ ( M ³⁺/ M ²⁺) depends on the enthalpy of hydration and the third ionisation enthalpy ( _i H₃ ). Manganese has the electronic configuration [ Ar ] 3 d ^5 4 s ^2 . The Mn ²⁺ ion has a stable half-filled 3 d ^5 configuration. Removing a third electron requires breaking this stable co