Assertion: `E^(@)` for `Mn^(3+)//Mn^(2+)` is more positive than `Cr^(3+)//Cr^(2+)`
Reason: The third ionisation energy of `Mn` is larger than that of `Cr`.

Options

A. If both assertion and reason are true and the reason is the correct explanation of the assertion.
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.
C. If assertion is true but reason is false.
D. If the assertion and reason both are false.

Answer

A

Explanation

`""_24Cr = 1s^2 , 2s^2 2p^6, 3s^2 3p^6 3d^5, 4s^1`
`""_25Mn = 1s^2, 2s^2 2p^6, 3s^2 3p^6 3d^5, 4s^2`
Reason : The `E^(0)` value is standard electrode potential which depends on ionization energy. Since `Mn^(2+)` gets a `d^5` configuration which is more stable than `Cr^(2+)` (`d^4` configuration), its` E^0` value is more positive than that of `Cr^(3+) //Cr^(2+)`. True
Assertion : True
`""_24 Cr^(2+) = 1s^2 , 2s^2 2p^6, 3s^2 3p^6 3d^4`
`""_25Mn^(2+) = 1s^2, 2s^2 2p^6, 3s^2 3p^6 3d^5`
Reason is the correct explanation of assertion.