Question

A solution of $HCl$ has a $pH=5$. If $1mL$ of it is diluted to $1$ litre, what will be the pH of the resulting solution?

Answer 1

$pH=5,\left[H^{+}\right]={10}^{-5}$
after dilution
$=\frac{{10}^{-5}}{1000}={10}^{-8}M$
$\left[H^{+}\right]={10}^{-8}+{10}^{-7}$
$pH=-\log \left[H^{+}\right]$

$pH=6.9586$