What different types of bonds are formed by chlorine with oxygen in perchloric acid?

Calculate the volume of fcc unit cell in $\mathrm{cm}^3$ if void volume of it is $4.16 \times 10^{-24} \mathrm{~cm}^3$.

Calculate standard enthalpy change of reaction

$$ \mathrm{C}_2 \mathrm{H}_{2(\mathrm{~g})}+\frac{5}{2} \mathrm{O}_{2(\mathrm{~g})} \longrightarrow 2 \mathrm{CO}_{2(\mathrm{~g})}+\mathrm{H}_2 \mathrm{O}_{(\mathrm{l})}, \text { if } $$

$$ \begin{aligned} & \Delta_{\mathrm{f}} \mathrm{H}^{\circ}\left(\mathrm{CO}_2\right)=-393 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ & \Delta_{\mathrm{f}} \mathrm{H}^{\circ}\left(\mathrm{H}_2 \mathrm{O}\right)=-286 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ & \Delta_{\mathrm{f}} \mathrm{H}^{\circ}\left(\mathrm{C}_2 \mathrm{H}_2\right)=227 \mathrm{~kJ} \mathrm{~mol}^{-1} \end{aligned} $$

Which from following formulae is used to find the $\left[\mathrm{OH}^{-}\right]$ion concentration of a weak monoacidic base?