A sample of `100 mL` of `0.10 M` weak acid, HA `(K_(a) = 1.0 xx 10^(-5))` is tirated with standard `0.10 M KOH`. What volume of `KOH` must have been addeed when the pH in the titration flask is 5

Options

A. `10`
B. `25`
C. `50`
D. `100`

Answer

C

Explanation

In the titration of weak acid and strong solution acts as acidic buffer, before the equivalence point.
`:. pH - pK_(a) + "log" (["salt"])/(["base"])`
Given pH `= pK_(a) = 5`
`:. ["salt"] = ["acid"]`
`:. 0.1 xx V_(a) = 10 - (0.1 xx V_(B))`
`:. V_(B) = 50 mL`