For a general nth order reaction `A to P` with initial concentration of the reactant 'a' and rate constant 'k', derive expression for time for `75%` completion of the reaction in terms of a, n and k.

Explanation

To derive the expression for the time required for 75% completion of a general nth order reaction \( A \to P \) with initial concentration \( a \) and rate constant \( k \), we can follow these steps:

### Step 1: Understand the Reaction
For a reaction \( A \to P \), if 75% of the reactant \( A \) has reacted, then 25% remains. Therefore, if the initial concentration of \( A \) is \( a \), the concentration of \( A \) at 75% completion will be:

\[ [A] = a - 0.75a = 0.25a \]
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