Lesson 12.1.1

12.1.1 Brønsted-Lowry acids, bases and conjugate pairs Quiz: Pearson Edexcel Chemistry, Unit 12

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 12.1.1, Brønsted-Lowry acids, bases and conjugate pairs: 20 multiple choice questions for the Pearson Edexcel Chemistry (9CH0), Unit 12: Acid-base Equilibria, written with Revision Ninja.

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The 20 questions

  1. What is a Bronsted-Lowry acid?

    • An electron pair acceptor
    • A species that releases hydroxide ions
    • A species that accepts a proton
    • A proton donor

  2. What is a Bronsted-Lowry base?

    • A species that always contains OH- ions
    • A proton acceptor
    • An electron pair donor only
    • A proton donor

  3. In the reaction HCl + H2O -> H3O+ + Cl-, which species is the Bronsted-Lowry base?

    • Cl-, because it is produced
    • H3O+, because it contains a proton
    • HCl, because it is the acid
    • H2O, because it accepts a proton

  4. In the reaction NH3 + H2O ⇌ NH4+ + OH-, which pair is a conjugate acid-base pair?

    • NH3 and OH-
    • H2O and NH4+
    • NH3 and H2O
    • NH4+ and NH3

  5. What is the conjugate base of HNO3?

    • NO3-
    • H2NO3+
    • NO2
    • HNO3-

  6. What is the conjugate acid of H2O when water acts as a base?

    • O2-
    • OH-
    • H3O+
    • H2

  7. Which statement describes acid-base reactions in terms of proton transfer?

    • No bonds break during acid-base reactions
    • Neutrons are transferred between species
    • Protons are transferred from the acid to the base
    • Electrons are transferred from the base to the acid only

  8. Which pair in the reaction HCO3- + H2O ⇌ H2CO3 + OH- is a conjugate pair with HCO3-?

    • H2CO3, its conjugate acid
    • OH-, its conjugate base
    • H2O, its conjugate acid
    • CO3 2-, its conjugate acid

  9. What is the definition of pH?

    • pH = log10[H+(aq)]
    • pH = 1 / [H+]
    • pH = [H+] x 10
    • pH = -log10[H+(aq)]

  10. A solution has [H+] = 1.0 x 10^-3 mol dm-3. What is its pH?

    • 11
    • -3
    • 3
    • 0.001

  11. Which statement describes a strong acid compared with a weak acid?

    • A strong acid has a higher pH than a weak acid at the same concentration, because it releases fewer protons
    • A strong acid is always concentrated, whereas a weak acid is always dilute in the laboratory
    • A strong acid is almost fully dissociated in water, while a weak acid is only partly dissociated
    • A weak acid donates more protons per molecule than a strong acid does when both are in water

  12. Which species acts as both a Bronsted-Lowry acid and a base in water?

    • H2O
    • Na+
    • NO3-
    • Cl-

  13. In the reaction CH3COOH + H2O ⇌ CH3COO- + H3O+, which species is a conjugate base?

    • CH3COOH
    • H3O+
    • CH3COO-
    • H2O

  14. Which statement about the Bronsted-Lowry definition is correct?

    • It defines acids as electron pair acceptors, which is the same as the Lewis definition of acidity
    • It applies to any species that donates or accepts a proton, including those in non-aqueous solvents
    • It requires the presence of hydroxide ions, since the acid must react with OH- to form water
    • It applies only to aqueous solutions of strong acids, so it cannot be used for weak acids or other solvents

  15. What is the pH of a solution in which [H+] = 2.5 x 10^-2 mol dm-3? (log10 2.5 = 0.40)

    • 2.40
    • 12.40
    • 0.40
    • 1.60

  16. What is meant by the term amphiprotic?

    • A species that is an electron pair donor only
    • A species that is always neutral
    • A species that donates two protons
    • A species that can both donate and accept a proton

  17. In the reaction NH4+ + OH- -> NH3 + H2O, which species acts as the Bronsted-Lowry acid?

    • NH4+, because it donates a proton
    • H2O, because it is neutral
    • NH3, because it is produced
    • OH-, because it accepts a proton

  18. What is the pH of a solution with [H+] = 1.0 x 10^-7 mol dm-3 at 298 K?

    • 14
    • 7
    • 0
    • 1

  19. Which description of a conjugate acid-base pair is correct?

    • They differ by exactly one proton
    • They differ by exactly one electron
    • They always have the same charge
    • They differ by one oxygen atom

  20. Which species is the conjugate acid of the carbonate ion, CO3 2-?

    • HCO3-
    • CO2
    • OH-
    • H2CO3 only

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