CHEM 120 Week 4 DQ: Acids & Bases
SECTION 1: DEFINITIONS OF ACIDS AND BASES
Question 1
According to the Arrhenius definition, an acid is a substance that:
A. Accepts a proton (H⁺)
B. Produces H⁺ ions (or H₃O⁺) when dissolved in water
C. Produces OH⁻ ions when dissolved in water
D. Donates an electron pair
Answer: B. Produces H⁺ ions (or H₃O⁺) when dissolved in water
Rationale: The Arrhenius definition states that an acid increases the concentration of H⁺
ions (or hydronium ions, H₃O⁺) in aqueous solution. A base produces OH⁻ ions in water.
This is the earliest and most restrictive definition of acids and bases.
Question 2
According to the Arrhenius definition, a base is a substance that:
A. Donates a proton (H⁺)
B. Accepts a proton (H⁺)
C. Produces OH⁻ ions when dissolved in water
D. Accepts an electron pair
Answer: C. Produces OH⁻ ions when dissolved in water
,Rationale: The Arrhenius definition states that a base increases the concentration of
OH⁻ ions in aqueous solution. Acids produce H⁺ ions. This definition is limited because it
only applies to aqueous solutions.
Question 3
Which of the following is an Arrhenius acid?
A. HCl
B. NaOH
C. NH₃
D. H₂O
Answer: A. HCl
Rationale: HCl (hydrochloric acid) produces H⁺ ions in water: HCl → H⁺ + Cl⁻. NaOH is a
base (produces OH⁻), NH₃ is a base (Brønsted-Lowry), and H₂O is amphoteric.
Question 4
Which of the following is an Arrhenius base?
A. HCl
B. NaOH
C. CH₃COOH
D. H₂SO₄
Answer: B. NaOH
Rationale: NaOH (sodium hydroxide) produces OH⁻ ions in water: NaOH → Na⁺ + OH⁻.
HCl and H₂SO₄ are acids, and CH₃COOH is a weak acid.
Question 5
, According to the Brønsted-Lowry definition, an acid is a substance that:
A. Donates a proton (H⁺)
B. Accepts a proton (H⁺)
C. Produces H⁺ ions in water
D. Accepts an electron pair
Answer: A. Donates a proton (H⁺)
Rationale: The Brønsted-Lowry definition is broader than Arrhenius. It defines an acid as
a proton (H⁺) donor and a base as a proton acceptor. This definition applies to non-
aqueous systems as well.
Question 6
According to the Brønsted-Lowry definition, a base is a substance that:
A. Donates a proton (H⁺)
B. Accepts a proton (H⁺)
C. Produces OH⁻ ions in water
D. Donates an electron pair
Answer: B. Accepts a proton (H⁺)
Rationale: A Brønsted-Lowry base is a proton acceptor. This allows substances like NH₃
(which has no OH⁻) to be classified as bases when they accept a proton.
Question 7
In the reaction: HCl + H₂O → Cl⁻ + H₃O⁺, which species is the Brønsted-Lowry acid?
A. HCl
B. H₂O
C. Cl⁻
D. H₃O⁺
Answer: A. HCl
SECTION 1: DEFINITIONS OF ACIDS AND BASES
Question 1
According to the Arrhenius definition, an acid is a substance that:
A. Accepts a proton (H⁺)
B. Produces H⁺ ions (or H₃O⁺) when dissolved in water
C. Produces OH⁻ ions when dissolved in water
D. Donates an electron pair
Answer: B. Produces H⁺ ions (or H₃O⁺) when dissolved in water
Rationale: The Arrhenius definition states that an acid increases the concentration of H⁺
ions (or hydronium ions, H₃O⁺) in aqueous solution. A base produces OH⁻ ions in water.
This is the earliest and most restrictive definition of acids and bases.
Question 2
According to the Arrhenius definition, a base is a substance that:
A. Donates a proton (H⁺)
B. Accepts a proton (H⁺)
C. Produces OH⁻ ions when dissolved in water
D. Accepts an electron pair
Answer: C. Produces OH⁻ ions when dissolved in water
,Rationale: The Arrhenius definition states that a base increases the concentration of
OH⁻ ions in aqueous solution. Acids produce H⁺ ions. This definition is limited because it
only applies to aqueous solutions.
Question 3
Which of the following is an Arrhenius acid?
A. HCl
B. NaOH
C. NH₃
D. H₂O
Answer: A. HCl
Rationale: HCl (hydrochloric acid) produces H⁺ ions in water: HCl → H⁺ + Cl⁻. NaOH is a
base (produces OH⁻), NH₃ is a base (Brønsted-Lowry), and H₂O is amphoteric.
Question 4
Which of the following is an Arrhenius base?
A. HCl
B. NaOH
C. CH₃COOH
D. H₂SO₄
Answer: B. NaOH
Rationale: NaOH (sodium hydroxide) produces OH⁻ ions in water: NaOH → Na⁺ + OH⁻.
HCl and H₂SO₄ are acids, and CH₃COOH is a weak acid.
Question 5
, According to the Brønsted-Lowry definition, an acid is a substance that:
A. Donates a proton (H⁺)
B. Accepts a proton (H⁺)
C. Produces H⁺ ions in water
D. Accepts an electron pair
Answer: A. Donates a proton (H⁺)
Rationale: The Brønsted-Lowry definition is broader than Arrhenius. It defines an acid as
a proton (H⁺) donor and a base as a proton acceptor. This definition applies to non-
aqueous systems as well.
Question 6
According to the Brønsted-Lowry definition, a base is a substance that:
A. Donates a proton (H⁺)
B. Accepts a proton (H⁺)
C. Produces OH⁻ ions in water
D. Donates an electron pair
Answer: B. Accepts a proton (H⁺)
Rationale: A Brønsted-Lowry base is a proton acceptor. This allows substances like NH₃
(which has no OH⁻) to be classified as bases when they accept a proton.
Question 7
In the reaction: HCl + H₂O → Cl⁻ + H₃O⁺, which species is the Brønsted-Lowry acid?
A. HCl
B. H₂O
C. Cl⁻
D. H₃O⁺
Answer: A. HCl
