Give reason for the folloiwng :
(a) `E_("value")^(@)` for `Mn^(3+)//Mn^(2+)` couple is much more positive than that of `Fe^(3+)//Fe^(2+)` couple.
(b) `Sc^(3+)` is colourless in aqueous solution whereas `Ti^(3+)` is coloured.

Explanation

### Step-by-Step Solution:

**(a)** To understand why the standard electrode potential \( E^\circ \) for the \( \text{Mn}^{3+}/\text{Mn}^{2+} \) couple is much more positive than that of the \( \text{Fe}^{3+}/\text{Fe}^{2+} \) couple, we need to analyze the electronic configurations of both ions.

1. **Electronic Configuration of \( \text{Mn}^{3+} \)**:
- Manganese (Mn) has an atomic number of 25. Its ground state electronic configuration is \( [Ar] 3d^5 4s^2 \).
- For \( \text{Mn}^{3+} \), we remove two 4s electrons and one 3d electron, resulting in \( 3d^4 \).

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