Lesson 3.1.12.1

3.1.12.1 Brønsted–Lowry acid–base equilibria in aqueous solution Quiz: AQA Chemistry, Unit 1

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.1.12.1, Brønsted–Lowry acid–base equilibria in aqueous solution: 20 multiple choice questions for the AQA Chemistry (7405), Unit 1: Physical chemistry, written with Revision Ninja.

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The 20 questions

  1. In Brønsted-Lowry theory, what is an acid?

    • A proton donor
    • A proton acceptor
    • An electron pair acceptor only
    • A substance that always contains oxygen and hydrogen

  2. In Brønsted-Lowry theory, what is a base?

    • A proton acceptor
    • A substance that always neutralises a metal oxide
    • A proton donor
    • An electron donor that always releases hydroxide ions

  3. What is the conjugate base of nitric acid, HNO3?

    • H3O^+
    • NO2^-
    • NH4^+
    • NO3^-

  4. What is the conjugate acid of ammonia, NH3?

    • H3O^+
    • NH2^-
    • NH4^+
    • OH^-

  5. What is the conjugate base of water, H2O?

    • O^2-
    • OH^-
    • H2O2
    • H3O^+

  6. What is the conjugate acid of water, H2O?

    • O^2-
    • H3O^+
    • OH^-
    • H2

  7. In the reaction HCl + H2O -> H3O^+ + Cl^-, which species is the Brønsted-Lowry acid?

    • Cl^-, because it accepts a proton from water
    • H2O, because it donates a proton to HCl
    • H3O^+, because it accepts a proton from HCl
    • HCl, because it donates a proton to water

  8. In the equilibrium NH3 + H2O <=> NH4^+ + OH^-, which species is the Brønsted-Lowry acid?

    • OH^-, because it accepts a proton from ammonium
    • NH4^+, because it accepts a proton from hydroxide
    • H2O, because it donates a proton to ammonia
    • NH3, because it donates a proton to water

  9. Which species can act as both a Brønsted-Lowry acid and a Brønsted-Lowry base?

    • SO4^2-, which can only donate protons
    • Cl^-, which can accept a proton but never donate one
    • HCO3^-, which can accept or donate a proton
    • Na^+, which can donate a proton to any base

  10. In the reaction NH3 + HCl -> NH4^+ + Cl^-, which species is the base?

    • HCl, because it accepts a proton from NH3
    • Cl^-, because it accepts a proton from ammonium
    • NH3, because it accepts a proton from HCl
    • NH4^+, because it donates a proton to chloride

  11. Why is hydrochloric acid described as a strong acid in water?

    • It does not dissociate at all in aqueous solution
    • It dissociates only partly, so most molecules remain as HCl
    • It is a weak acid that gains protons from the solvent
    • It dissociates completely into hydrogen ions and chloride ions

  12. Why is ethanoic acid described as a weak acid?

    • It dissociates only slightly in water, so the equilibrium lies far to the left
    • It is a strong acid that is only partly neutralised by bases
    • It dissociates completely, but it produces very few hydrogen ions
    • It does not donate protons at all in aqueous solution

  13. Which of these is a conjugate acid-base pair?

    • HCl and H2O
    • HCl and Cl^-
    • NH3 and OH^-
    • H3O^+ and OH^-

  14. Which species forms when the ethanoate ion, CH3COO^-, accepts a proton?

    • CH3COOH
    • CH3COO^2-
    • CH3OH
    • CH3CO^+

  15. Why does the equilibrium CH3COOH + H2O <=> CH3COO^- + H3O^+ lie to the left?

    • Water is a strong base, so it removes all of the protons from ethanoic acid
    • The ethanoate ion is a strong acid, so it reacts back to ethanoic acid completely
    • Ethanoic acid donates protons completely, so products are favoured at equilibrium
    • Ethanoic acid donates protons only partly, so reactants are favoured at equilibrium

  16. In aqueous solution, which process do acid-base equilibria involve?

    • The transfer of oxygen atoms between species
    • The formation of covalent bonds between metal ions only
    • The transfer of electrons between species
    • The transfer of protons between species

  17. In the reaction HNO3 + H2O -> H3O^+ + NO3^-, which species is the Brønsted-Lowry base?

    • NO3^-, because it donates a proton to water
    • H3O^+, because it donates a proton to nitrate
    • HNO3, because it accepts a proton from water
    • H2O, because it accepts a proton from nitric acid

  18. Which species is the conjugate acid of the hydrogen phosphate ion, HPO4^2-?

    • PO4^3-
    • HPO4^3-
    • H3PO4
    • H2PO4^-

  19. What is the relationship between the acid and its conjugate base?

    • They differ by exactly one oxygen atom, the conjugate base having one fewer oxygen
    • They differ by exactly one proton, the conjugate base having one less H+
    • They differ by exactly one electron, the conjugate base having one more electron
    • They are identical species that exist only in different phases

  20. In the reaction of ammonia with water, NH3 + H2O <=> NH4^+ + OH^-, why is ammonia described as a weak base?

    • It donates a proton to water completely, forming OH^- ions
    • It accepts a proton from water only partly, so the equilibrium lies far to the left
    • It accepts a proton from water completely, so the equilibrium lies far to the right
    • It is a strong base because all of its molecules form ammonium ions

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