Increasing order of solubility of AgCl in (i) $\mathrm{H}_2 \mathrm{O}$, (ii) 1 M NaCl (aq.), (iii) 1 M CaCl 2 (aq.) and (iv) $1 \mathrm{M}~ \mathrm{NaNO}_3$ (aq.) solution

As per the following equation, 0.217 g of HgO (molecular mass $=217 \mathrm{~g} \mathrm{~mol}^{-1}$ ) reacts with excess iodide. On titration of the resulting solution, how many mL of 0.01 M HCl is required to reach the equivalence point?

$\mathrm{HgO}+4 \mathrm{I}^{-}+\mathrm{H}_2 \mathrm{O} \longrightarrow \mathrm{HgI}_4{ }^{2-}+2 \mathrm{OH}^{-}$

At 25$$^\circ$$C, the ionic product of water is 10$$^{-14}$$. The free energy change for the self-ionization of water in kCal mol$$^{-1}$$ is close to

Equal volumes of aqueous solution of $$0.1(\mathrm{M}) \mathrm{HCl}$$ and $$0.2(\mathrm{M}) \mathrm{H}_2 \mathrm{SO}_4$$ are mixed. The concentration of $$\mathrm{H}^{+}$$ ions in the resulting solution is