What is the $pH$ of a $0.001 \, M \, KOH$ solution at $90 \, ^\circ C$ $(K_w = 10^{-12})$?

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 $\log 2 = 0.30$):

The concentration in $M$ of $OH^{-}$ in $0.001 \ M$ $H_2SO_4$ is

For a solution of $HCl$ assuming complete ionization,the $pH = 1$. Find the normality of a $H_2SO_4$ solution having the same $pH$.

$40 \, mg$ of pure sodium hydroxide is dissolved in $10 \, L$ of distilled water. The $pH$ of the solution is

In a solution of $pH = 5$,more acid is added in order to reduce the $pH$ to $2$. The increase in hydrogen ion concentration is $......$ times.