Question

The pH of a mixture of 100 ml of 0.5 HCl and 100 ml of 0.6 N NaOH solution is:

• A. 10.5
• B. 1.3
• C. 12.7
• D. 4.7

Answer 1

The correct option is C 12.7

The formula for the hydroxide ion concentration is,
$[OH{]}^{-}=\frac{N_b{V}_b-N_a{V}_a}{V_a+V_b}$.
Substitute values in the above expression,
$[OH{]}^{-}=\frac{0.6\times 0.1-0.5\times 0.1}{0.1+0.1}=0.05$ M.
$pOH=-log[OH{]}^{-}=-log0.05=1.3$.
$pH=14-pOH=14-1.3=12.7$.