Paper 1 Q29 — Sulfuric acid is diprotic

Acid–base — H₂SO₄ provides two moles of H⁺ per mole

What the examiners said

“Many did not consider the diprotic nature of sulfuric acid and selected statement 3 as correct, as well as statement 1.”

Try the question (reconstruction)

Equal volumes and equal concentrations of HCl and H₂SO₄ are each fully neutralised. How does the amount of NaOH needed compare?

Examiner report: “Candidates overlooked that one mole of H₂SO₄ supplies two moles of H⁺.”

Explore — count the protons

Titrate equal amounts of a monoprotic and a diprotic acid with the same NaOH. Watch how many moles of base each consumes to reach neutrality.

Acid concentration (mol dm⁻³): 0.10

Moles of NaOH = moles of acid × (protons per molecule). For H₂SO₄ that multiplier is 2.

Original reconstruction inspired by the misconceptions described in the Singapore-Cambridge GCE A-Level H2 Chemistry 9729 November 2023 Examiner Report. Not the actual examination question. For classroom exploration.

Made by lookang, using Claude Fable 5. More resources: iwant2study.org