What will be the `pH` of a solution formed by mixing `40 ml` of `0.10 M HCl` with `10 ml` of `0.45 M NaOH`?

Options

A. 12
B. 10
C. 8
D. 6

Answer

A

Explanation

M.eq. of 0.01 M HCl `= (0.10)/(1000) xx 40 = 0.004 M`
M.eq. of 0.45 M NaOH `= (0.45 xx 10)/(1000) = 0.0045 M`
Now left `[OH^(-)] = 0.0045 - 0.004 = 5 xx 10^(-4)M`
Total volume = 50 ml
`[OH^(-)] = (5 xx 10^(-4))/(50) xx 1000, [OH^(-)] = 1 xx 10^(-2)`
`pOH = 2, pH = 14 - pOH = 12`.