Insufficient equilibrium data for [HSO4-]

Steps:

• H2SO4 dissociates completely, giving initial [HSO4-] = 1.96 mol dm⁻³ and [H⁺] = 1.96 mol dm⁻³.
• The second equilibrium HSO₄⁻ ⇌ SO₄²⁻ + H⁺ requires K to solve for x in Ka = (1.96 + x)x / (1.96 - x).
• No numerical value for K is provided in the problem.
• Not enough information to calculate the equilibrium [HSO4-] = 1.96 - x.

Why C is correct:

• Not enough information; K value is missing, preventing numerical solution despite C being stated as correct.

Why the others are wrong:

• A, B, D: All require the missing K for validation, but cannot be computed without it.

Final answer: Not enough information.