Question

The pH of a solution obtained by mixing equal volumes of $\frac{N}{10}NaOH$ and $\frac{N}{20}HCl$

• A. 13.4
• B. 12.4
• C. 7.6
• D. 1.6

Answer 1

Answer: (B)

Let the volume of $NaOH$ used $=V=$ volume of $HCl$ used.
Concentration of mixture $[O{H}^{-}]$
$\frac{0.1V-0.05V}{(V+V)}$
$[\because$ Milliequivalent of $NaOH$ is in excess.$]$
$\frac{V(0.1+0.05)}{2V}$
$=\frac{0.05}{2}=0.025$
$pOH=-\log [O{H}^{-}]=-\log (0.025)$
$=1.602$
$\therefore pH=14-1.602=12.4$