Questions on Brønsted-Lowry Acids and Bases
20 Multiple-Choice Questions on Brønsted-Lowry Acids and Bases
1. According to the Brønsted-Lowry definition, an acid is a substance that:
A) Produces OH⁻ in solution
B) Accepts a proton
C) Donates a proton
D) Forms a salt with metals
E) Neutralizes bases by precipitation
2. A Brønsted-Lowry base is defined as a substance that:
A) Donates electrons
B) Donates protons
C) Accepts protons
D) Produces hydronium ions
E) Neutralizes acids through dissociation
3. Which of the following is a Brønsted-Lowry acid in the reaction:
HCl + H₂O → H₃O⁺ + Cl⁻
A) H₂O
B) Cl⁻
C) HCl
D) H₃O⁺
E) OH⁻
4. Which of the following acts as a Brønsted-Lowry base in the same reaction?
HCl + H₂O → H₃O⁺ + Cl⁻
A) H₂O
B) HCl
C) Cl⁻
D) H₃O⁺
E) H⁺
5. In the reaction NH₃ + H₂O ⇌ NH₄⁺ + OH⁻, what is the Brønsted-Lowry base?
A) NH₄⁺
B) H₂O
C) OH⁻
D) NH₃
E) H₃O⁺
6. Which of the following can act as both a Brønsted-Lowry acid and base (amphiprotic)?
A) HCl
B) H₂O
C) NH₄⁺
D) NaOH
E) CH₄
7. What is the conjugate acid of NH₃?
A) NH₄⁺
B) NH₂⁻
C) H₃O⁺
D) OH⁻
E) H₂
8. What is the conjugate base of H₂SO₄?
A) SO₄²⁻
B) HSO₄⁻
C) OH⁻
D) H₃O⁺
E) H₂SO₃
9. A conjugate acid-base pair differs by:
A) A proton
B) An electron
C) An oxygen atom
D) A hydroxide ion
E) A neutron
10. Which of the following is not a Brønsted-Lowry base?
A) OH⁻
B) NH₃
C) H₂O
D) HCl
E) CH₃COO⁻
11. In the reaction HCOOH + H₂O ⇌ H₃O⁺ + HCOO⁻, which is the conjugate base?
A) HCOOH
B) H₂O
C) H₃O⁺
D) HCOO⁻
E) OH⁻
12. When HCl reacts with NH₃, what is the conjugate acid of NH₃?
A) NH₂⁻
B) NH₄⁺
C) H₂O
D) H₃O⁺
E) Cl⁻
13. Which of the following reactions demonstrates Brønsted-Lowry acid-base behavior?
A) NaCl → Na⁺ + Cl⁻
B) CH₃COOH + H₂O ⇌ CH₃COO⁻ + H₃O⁺
C) CaCO₃ → CaO + CO₂
D) H₂ + Cl₂ → 2HCl
E) CO₂ + H₂O → H₂CO₃
14. Which of the following substances is capable of accepting a proton?
A) HCl
B) H₂O
C) NH₄⁺
D) H₂SO₄
E) HNO₃
15. The Brønsted-Lowry definition of acids and bases is broader than the Arrhenius definition because:
A) It includes redox reactions
B) It only applies to aqueous solutions
C) It does not involve ions
D) It allows reactions without water
E) It excludes proton transfer
16. Which is the conjugate acid of the Brønsted-Lowry base H₂O?
A) OH⁻
B) H₃O⁺
C) H₂
D) H₂O₂
E) O²⁻
17. The conjugate base of H₂CO₃ is:
A) CO₃²⁻
B) HCO₃⁻
C) H₃O⁺
D) OH⁻
E) H₂O
18. What is the conjugate acid of H₂O in a reaction?
A) OH⁻
B) O²⁻
C) H₃O⁺
D) H⁺
E) H₂
19. Which of the following is the Brønsted-Lowry base in the reaction:
HS⁻ + H₂O ⇌ H₂S + OH⁻?
A) H₂O
B) HS⁻
C) OH⁻
D) H₂S
E) H⁺
20. Which of the following is an example of an amphiprotic substance under the Brønsted-Lowry model?
A) NH₄⁺
B) H₂O
C) Cl⁻
D) Na⁺
E) CH₄
Answer Key with Explanations
1. C – A Brønsted-Lowry acid is a proton (H⁺) donor.
2. C – A Brønsted-Lowry base accepts a proton (H⁺).
3. C – HCl donates a proton to water; it is the acid.
4. A – H₂O accepts the proton, acting as the base.
5. D – NH₃ accepts a proton and becomes NH₄⁺.
6. B – H₂O can donate or accept protons = amphiprotic.
7. A – NH₄⁺ is formed when NH₃ gains a proton.
8. B – HSO₄⁻ is the conjugate base of H₂SO₄ after losing one H⁺.
9. A – Conjugate acid-base pairs differ by a single proton (H⁺).
10. D – HCl is a strong acid, not a base.
11. D – HCOO⁻ is what’s left after HCOOH donates a proton.
12. B – NH₄⁺ is formed when NH₃ accepts a proton from HCl.
13. B – This reaction shows acid-base behavior with proton transfer.
14. B – H₂O can accept H⁺ and become H₃O⁺.
15. D – Brønsted-Lowry includes non-aqueous reactions and solvents.
16. B – H₃O⁺ is formed when H₂O accepts a proton.
17. B – HCO₃⁻ is formed when H₂CO₃ loses one proton.
18. C – H₃O⁺ is the protonated form of water.
19. B – HS⁻ accepts a proton to become H₂S.
20. B – H₂O can both donate and accept protons = amphiprotic.
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