Hydrogen ion concentration of an aqueous solution is $1 \times 10^{-4} \ M$. The solution is diluted with an equal volume of water. The hydroxyl ion concentration of the resultant solution in terms of $mol \ dm^{-3}$ is

Arrange the following resultant mixtures in increasing order of their pH values:
$A$. $10 \text{ mL } 0.2 \text{ M } Ca(OH)_2 + 25 \text{ mL } 0.1 \text{ M } HCl$
$B$. $10 \text{ mL } 0.01 \text{ M } H_2SO_4 + 10 \text{ mL } 0.01 \text{ M } Ca(OH)_2$
$C$. $10 \text{ mL } 0.1 \text{ M } H_2SO_4 + 10 \text{ mL } 0.1 \text{ M } KOH$
Choose the correct answer from the options given below:

The first and second dissociation constants of a diprotic acid $H_2A$ are $1.0 \times 10^{-5}$ and $5.0 \times 10^{-10}$ respectively. The overall dissociation constant of the acid is:

$A$ solution contains $8 \, g$ of $NaOH$ and $4.9 \, g$ of $H_2SO_4$ in $1 \, L$ of solution. What is its $pH$?

Calcium lactate is a salt of a weak organic acid. $A$ $0.5 \ L$ saturated solution of calcium lactate contains $0.13 \ mol$ of the salt. If the $p^{OH}$ of the solution is $5.6$,what will be the $K_a$ of lactic acid,assuming complete dissociation of the salt?

For the reaction in aqueous solution $Zn^{2+} + X^{-} \rightleftharpoons ZnX^{+}$,the $K_{eq}$ is greatest when $X$ is