Aqueous solution of $HCl$ has the $pH = 4$. Its molarity would be (in $, M$)

$25 \ mL$ of $0.1 \ M$ $HCl$ solution is diluted till $500 \ mL$. Calculate the $pH$ of the dilute solution. (in $.3$)

Calculate the $pH$ of the following solutions:
$(a)$ $2 \,g$ of $TlOH$ dissolved in water to give $2 \,L$ of solution.
$(b)$ $0.3 \,g$ of $Ca(OH)_2$ dissolved in water to give $500 \,mL$ of solution.
$(c)$ $0.3 \,g$ of $NaOH$ dissolved in water to give $200 \,mL$ of solution.
$(d)$ $1 \,mL$ of $13.6 \,M \,HCl$ is diluted with water to give $1 \,L$ of solution.

$75 \ mL$ of $0.2 \ M \ HCl$ is mixed with $25 \ mL$ of $1 \ M \ HCl$. To this solution, $300 \ mL$ of distilled water is added. What is the $pH$ of the resultant solution?

The $pH$ of a $0.05 \,M$ solution of a strong dibasic acid $(H_2A)$ is:

At $298 \, K$,what is the concentration of hydrogen ions in a $10^{-8} \, M \, HCl$ aqueous solution? $(K_W = 10^{-14})$