Question

Calculate the pH of a solution prepared by mixing 2.0 ml of a strong acid $\left(HCl\right)$ solution of pH 3.0 and 2.0 ml of a strong base $\left(NaOH\right)$ of pH 11.0

Answer 1

Number of milliequivalents of $HCl$
$=2\times {10}^{-3}$
We know that pH + pOH = 14.
$\Rightarrow 11+pOH=14$
$\Rightarrow pOH=3$
$\Rightarrow [OH{]}^{-}={10}^{-3}M$
2 ml of ${10}^{-3}\text{M}NaOH=2\times {10}^{-3}$
Number of milliequivalents of $NaOH$ = $2\times {10}^{-3}$
The resulting solution is neutral since the number of meq of acid and base are the same.
The pH would be 7.