When `2.5 mL` of `2//5M` weak monoacidic base `(K_(b) = 1 xx 10^(-12) at 25^(@)C)` is titrated with `2//15 M HCI` in water at `25^(@)C` the concentration of `H^(o+)` at equivalence point is `(K_(w) = 1 xx 10^(-14) at 25^(@)C)`

Options

A. `3.7xx10^(-13)M`
B. `3.2xx10^(-7)M`
C. `3.2xx10^(-2)M`
D. `2.7xx10^(-2)M`

Answer

D

Explanation

The base is very weak, the cations of the salt formed at the equivalence point shall undergo hydrolysis to a greater extent and so the degree of hydrolysis, h cannot be neglected in comparison to 1. Now apply
`Kh=(Ch^(2))/(1-h)=K_(w)/K_(b),C=0.1M,[H^(+)]=Ch`