How many moles of $HCl$ must be removed from $1 \ L$ of an aqueous $HCl$ solution to change its $pH$ from $2$ to $3$?

$pH$ value of $0.001 \ M \ NaOH$ solution is $..... .$

The $pH$ of $10^{-7} \ N \ HCl$ is

An aqueous solution of $HCl$ with $pH \ 1.0$ is diluted by adding an equal volume of water (ignoring the dissociation of water). The $pH$ of the $HCl$ solution would be (Given $\log 2 = 0.30$):

What will be the resultant $pH$ when $100 \ mL$ of an aqueous solution of $HCl$ $(pH = 2)$ is mixed with $200 \ mL$ of an aqueous solution of $NaOH$ $(pH = 12)$?

Calculate the $pH$ of $1.0 \times 10^{-8} \ M \ NaOH$ solution.