What is the `pH` of the resulting solution when equal volumes of `0.1 M NaOH` and `0.01 M HCl` are mixed?

Options

A. `2.0`
B. `7.0`
C. `1.04`
D. `12.65`

Answer

D

Explanation

when equal volumes of acid and base solutions are mixed, the molarity of each one of them is reduced to half.
Molarity of NaOH solution after mixing =0.05 M `[OH^(-)]` in solution after mixing = 0.05 M
Molarity of HCI solution after mixing =0.005 M
`[H^(+)]` in solution after mixing =0.005 M
`[OH^(-)]` in solution after neutralisation =(0.05 -0.005)
= 0.045 M
`pOH =- log (0.045) =- log (4.5 xx 10^(-2))`
`=(2- log 4.5) =2 - 0.6532 =1.3468`
`pH =14 -1.3468 =12.65`