The solubility of $\mathrm{Sr}(\mathrm{OH}{)}_2$ at $298 \mathrm{K}$is $19.23 \mathrm{g}/\mathrm{L}$ of solution. Calculate the concentrations of strontium and hydroxyl ions and the pH of the solution.

$50 \mathrm{mL} 0.04 \mathrm{M}$ calcium nitrate solution is added to $150 \mathrm{mL}$ of $0.08 \mathrm{M}$ ammonium sulphate. Will a precipitate of calcium sulphate form or not?

${\mathrm{K}}_{\mathrm{sp}} =0.4\times {10}^{-5}$

Which of the following are Lewis acids?

${\mathrm{H}}_2\mathrm{O}, {\mathrm{BF}}_3, {\mathrm{H}}^{+} \mathrm{and} {\mathrm{NH}}_4^{+}$

The value of ${\mathrm{K}}_{\mathrm{c}}$ in the reaction, $2\mathrm{A}\rightleftharpoons \mathrm{B}+\mathrm{C}$ is $2\times {10}^{-3}$. At a given time, the composition of reaction mixture is $\mathrm{A}=\mathrm{B}=\mathrm{C}=3\times {10}^{-4} \mathrm{M}$. In which direction the reaction will proceed?