Tutoring hours from just $25! N26 IB exam session special: Biology, Chemistry and Economics $25, Maths SL and English $35, until 12 November.
LimeAdmissionsPractice

Practice · Chemistry · 2025 syllabus · R3.1

IB Chemistry R3.1 Proton transfer reactions: practice questions

13 exam-style questions on R3.1 Proton transfer reactions, SL and HL, 8 marked HL: 7 multiple choice, 2 data-based and 4 structured. Each one comes with the mark scheme, a model answer and the reasoning behind every mark. Free with your email.

Try one

R3.1-01 · Paper 1A style · multiple choice · 1 mark

Acting as acid and base

Which species can act as both a Brønsted–Lowry acid and a Brønsted–Lowry base in water? [1]

  1. SO42−
  2. HSO4−
  3. NH4+
  4. H3O+
Show the answer and the reasoning

Answer: B. B is correct. HSO4− can donate a proton (forming SO42−) and accept one (forming H2SO4). A has no proton to donate, so it can only be a base. C has no lone pair left to accept a proton. D still has one lone pair, but as a positive ion it does not accept a second proton in water. Both act only as acids.

The other 12 open with your email, with the same mark scheme and reasoning.

Open the questions

Free while in beta. Type your email and every question opens straight away.

Signed up before, here or for our past-paper links? Use the same email and you are straight in, on any device. You also get our occasional email on IB exam technique and what we offer. Unsubscribe in any message. How the address is handled.

You are in. Every R3.1 question is open, with your progress.

Open the R3.1 questions

The 13 questions in R3.1

  1. R3.1-01 Acting as acid and basePaper 1A style · multiple choice · 1 mark
  2. R3.1-02 Hydroxide ions from pHPaper 1A style · multiple choice · 1 mark · HL
  3. R3.1-03 What a pH change meansPaper 1A style · multiple choice · 1 mark
  4. R3.1-04 Salt with the highest pHPaper 1A style · multiple choice · 1 mark · HL
  5. R3.1-05 Why a strong acid has lower pHPaper 1A style · multiple choice · 1 mark
  6. R3.1-06 Indicator for a weak base titrationPaper 1A style · multiple choice · 1 mark · HL
  7. R3.1-07 pH of a bufferPaper 1A style · multiple choice · 1 mark · HL
  8. R3.1-08 Standardizing potassium hydroxidePaper 1B style · data-based · 7 marks
  9. R3.1-09 Ka of methanoic acid from pHPaper 1B style · data-based · 6 marks · HL
  10. R3.1-10 A weak acid titration curvePaper 2 style · structured question · 6 marks · HL
  11. R3.1-11 An ammonia bufferPaper 2 style · structured question · 5 marks · HL
  12. R3.1-12 pH of a weak basePaper 2 style · structured question · 5 marks · HL
  13. R3.1-13 Strong and weak acids comparedPaper 2 style · structured question · 6 marks

More of R3 What are the mechanisms of chemical change?

Every Chemistry topic · Biology, Chemistry and Economics

Stuck on a topic?

Go through it with a tutor, the first 30 minutes free.

Biology, Chemistry and Economics, one to one, online.

Book the free session

Free live sessions

Join 100+ IB students in our free live sessions.

Exam technique for IB Biology, Chemistry and Economics, live on Zoom. Follow the calendar and every new session reaches you.

See the free sessions →

Every Biology and Chemistry question here is original, written for practice in the style of the papers set since the 2025 syllabus, with invented data. Developed independently from the International Baccalaureate Organization, which has not endorsed it. Found a mistake? Email vytis@limeadmissions.com with the question id.