Ionic Equilibrium – JEE Main ChemistryPractice Questions & PYQs

Buffer solutions rely on the presence of a weak acid and its conjugate base or a weak base and its conjugate acid to resist pH changes. Hydrochloric acid is a strong acid that dissociates fully in solution, and sodium chloride is a salt derived from a strong acid and a strong base, meaning neither component has the chemical property required to buffer the solution. Because the mixture is effectively a solution of a strong acid, the solution is acidic and therefore possesses a $\mathrm{pH} < 7$.

According to the Bronsted-Lowry theory, a chemical species is classified as amphoteric if it can function as both a proton donor and a proton acceptor. The $(\mathrm{HSO}_4)^{-}$ ion is a classic example of this behavior because it possesses both a removable proton and the capacity to accommodate an additional one. Consequently, it acts as a Bronsted base by accepting a proton to form $\mathrm{H}_2\mathrm{SO}_4$ and as a Bronsted acid by donating a proton to yield the $(\mathrm{SO}_4)^{2-}$ ion, a dual functionality not shared by the other species provided.

The dissociation of a sparingly soluble salt like PbS into its ions, $\text{Pb}^{2+}$ and $\text{S}^{2-}$, establishes the relationship K_{sp} = \[\text{Pb}^{2+}]$$[\text{S}^{2-}]$ = S^2$. By setting$S^2 = 8 \times 10^{-28}$, we determine the solubility as$S = \sqrt{8 \times 10^{-28}}$. Using the given value for the square root of 2, this calculates to$S = 2 \times 1.41 \times 10^{-14} = 2.82 \times 10^{-14}$mol L^-1. Converting this to scientific notation with an exponent of 10^-16 results in$282 \times 10^{-16}$ mol L^-1, which identifies x as 282.