How many litres of water must be added to $1 \ L$ of an aqueous solution of $HCl$ with a $pH$ of $1$ to create an aqueous solution with $pH$ of $2$?

If $100 \, mL$ of a solution with $pH = 3$ is mixed with $400 \, mL$ of another solution with $pH = 3$,what will be the $pH$ of the resulting mixture?

Which of the following will have the highest $pH$?

If the $pH$ of a solution of an alkali metal hydroxide is $13.6$,the concentration of hydroxide is

Following solutions were prepared by mixing different volumes of $NaOH$ and $HCl$ of different concentrations:
$a. \; 60 \; mL \; \frac{M}{10} \; HCl + 40 \; mL \; \frac{M}{10} \; NaOH$
$b. \; 55 \; mL \; \frac{M}{10} \; HCl + 45 \; mL \; \frac{M}{10} \; NaOH$
$c. \; 75 \; mL \; \frac{M}{5} \; HCl + 25 \; mL \; \frac{M}{5} \; NaOH$
$d. \; 100 \; mL \; \frac{M}{10} \; HCl + 100 \; mL \; \frac{M}{10} \; NaOH$
$pH$ of which one of them will be equal to $1$?

The $pH$ of $0.1 \ M \ NaOH$ is