Multiple$-$choice questions

The solubility product expression for calcium fluoride, $Ca{F}_2$ is

$($a$)[C{a}^2][F^2]$

$($b$)[C{a}^2][F]$

$($c$)[C{a}^{2+}][F{]}^2$

$($d$)[C{a}^{2-}{]}^2[F]$

What is the approximate $pH$ of a $KHC{O}_3$ solution?

$($a$)7$

$($b$)13\mathrm{.}5$

$($c$)8\mathrm{.}5$

$($d$)5\mathrm{.}2$

Which of these pairs of elements consists of isotopes?

$($a$)Ar$ and $K$

$($b$){?}^{14}C$ and ${?}^{14}N$

$($c$){?}^{15}0$ and ${?}^{27}0$

$($d$){?}_{29}^{65}Cu$ and ${?}_{30}^{66}Zn$