CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
The hydrogen sulfate ion, HSO4−, is placed in pure water. Data at 25∘C: Ka1(H2SO4)≈1 (first dissociation is essentially complete); Ka2(HSO4−)=1.2×10−2; Kw=1.0×10−14.
Parts
(a) Write two distinct proton-transfer equations between HSO4− and liquid water: one in which HSO4− donates a proton and one in which it accepts a proton.
(b) Derive an equilibrium constant for each reaction written in part (a) using only the tabulated Ka values and Kw as needed. Show all algebraic steps.
(c) Compare the numerical values obtained in part (b) and determine which of the two reactions predominates in an aqueous solution containing only HSO4− and water. Justify your conclusion quantitatively and qualitatively.
(d) Based on your analysis, specify the role played by liquid water (acid or base) in the predominant reaction and explain how the calculated equilibrium constants support your identification.