The solubility product of $\mathrm{PbI}_2$ is $2.8 \times 10^{-8}$. Calculate its solubility in $\mathrm{mol} \mathrm{dm}^{-3}$.

Which from the following buffers is used for precipitation of cations of IIIA group in qualitative analysis?

The dissociation constant of weak monoacidic base is $1.8 \times 10^{-5}$. Calculate the degree of dissociation in 0.02 M solution.

Calculate the pH of buffer solution containing 0.12 M weak acid and 0.48 M of its salt with strong base if $\mathrm{pK}_{\mathrm{a}}$ is 3.82 .