Weight of $Ca(OH)_2$ needed to prepare $250 \ mL$ of solution with $pH = 13$. (in $g$)

Which of the following solutions will have the maximum $pH$?

What is the normality of an aqueous solution of $H_2SO_4$ having $pH = 1$ (in $N$)?

Calculate the $pH$ of a $0.37 \ g$ $Ca(OH)_2$ solution in $200 \ mL$ of water. (Atomic masses: $Ca = 40, O = 16, H = 1$)

The $pH$ of a $H_2SO_4$ solution is $5.0$. If more $H_2SO_4$ is added to this solution,the $pH$ becomes $2.0$. The concentration of $H^{+}$ ions will become how many times the initial concentration?

The $pH$ of the solution obtained by mixing $100 \ mL$ of a solution of $pH=3$ with $400 \ mL$ of a solution of $pH=4$ is