14.1 Multiple Choice
1) In an Arrhenius acid-base context, the compounds KOH, H2SO4, and HNO3 when dissolved in water, function respectively as a(n) ________.
A) base, acid and acid
B) acid, base and base
C) base, acid and base
D) base, base and acid
2) Each of the following can act like a Bronsted-Lowry acid and Bronsted-Lowry base except:
A) NH4+
B) H2PO4-
C) HCO3-
D) HS-
3) A Bronsted-Lowry acid is defined as a substance that ________.
A) increases the [H+] concentration when placed in water
B) decreases the [H+] concentration when placed in water
C) acts as a proton donor in any system
D) acts as a proton acceptor in any system
4) According to the Bronsted-Lowry theory, a base is ________.
A) a hydronium ion donor
B) a proton donor
C) a proton acceptor
D) a hydroxide ion acceptor
5) Which of the following could not be a Bronsted-Lowry acid?
A) HF
B) HC2H3O2
C) CN−
D) HS−
6) The Bronsted-Lowry acid and base for the reaction
NH4+ + CN− –> NH3 + HCN are, respectively, ________.
A) NH3 and CN−
B) NH4+ and HCN
C) CN− and HCN
D) NH4+ and CN−
7) Which of the following is incorrectly classified as an acid, a base, a salt, or an amphoteric species?
A) H2Sacid
B) NH4+base
C) LiOHbase
D) HS−amphoteric
8) Which of the following is not a conjugate acid/base pair?
A) PH4+/PH3
B) H2O/OH−
C) HSO4−/SO42−
D) S2−/H2S
9) From the choices below, identify a conjugate acid-base pair. (The acid is listed first in the pair.)
H2PO4− + S2− –> HS− + HPO42−
Acid Conjugate Base
A) S-2 HS-
B) H2PO4-S-2
C) H2PO4-HPO4-2
D) HS-H2PO4-
10) Which of the following pairs of acids and conjugate bases is incorrectly labeled?
Acid Conjugate Base
A) HSO4-SO4-2
B) HFO2HFO3
C) HSO3-SO3-2
D) NH4+NH3
The Correct Answer and Explanation is :
Here are the answers with brief explanations for each question:
1) In an Arrhenius acid-base context, the compounds KOH, H2SO4, and HNO3 when dissolved in water, function respectively as a(n) ________.
Answer: A) base, acid, and acid
Explanation:
- KOH is a base because it dissociates to form OH⁻ ions in water.
- H₂SO₄ (sulfuric acid) and HNO₃ (nitric acid) are acids because they dissociate to produce H⁺ ions in water.
2) Each of the following can act like a Bronsted-Lowry acid and Bronsted-Lowry base except:
Answer: D) HS⁻
Explanation:
- NH₄⁺ can donate a proton (acid) or accept a proton (base).
- H₂PO₄⁻ can donate a proton (acid) or accept a proton (base).
- HCO₃⁻ can donate a proton (acid) or accept a proton (base).
- HS⁻ only accepts protons (base), but it does not donate protons, so it can’t act as an acid.
3) A Bronsted-Lowry acid is defined as a substance that ________.
Answer: C) acts as a proton donor in any system
Explanation:
- A Bronsted-Lowry acid is a proton donor, meaning it donates H⁺ ions (protons) in a reaction.
4) According to the Bronsted-Lowry theory, a base is ________.
Answer: C) a proton acceptor
Explanation:
- A Bronsted-Lowry base is defined as a substance that accepts a proton (H⁺).
5) Which of the following could not be a Bronsted-Lowry acid?
Answer: C) CN⁻
Explanation:
- CN⁻ (cyanide ion) is a base, not an acid. It can accept protons, but it cannot donate them, which is what acids do.
6) The Bronsted-Lowry acid and base for the reaction: NH₄⁺ + CN⁻ → NH₃ + HCN are, respectively, ________.
Answer: D) NH₄⁺ and CN⁻
Explanation:
- NH₄⁺ donates a proton (acting as an acid), while CN⁻ accepts the proton (acting as a base).
7) Which of the following is incorrectly classified as an acid, a base, a salt, or an amphoteric species?
Answer: B) NH₄⁺ base
Explanation:
- NH₄⁺ is an acid, not a base. It can donate a proton, making it a Bronsted-Lowry acid.
8) Which of the following is not a conjugate acid/base pair?
Answer: D) S²⁻/H₂S
Explanation:
- S²⁻ is the conjugate base of HS⁻, not H₂S, so S²⁻/H₂S is not a conjugate acid-base pair.
9) From the choices below, identify a conjugate acid-base pair. (The acid is listed first in the pair.)
Answer: C) H₂PO₄⁻/HPO₄²⁻
Explanation:
- H₂PO₄⁻ (dihydrogen phosphate) donates a proton to form HPO₄²⁻ (hydrogen phosphate), making them a conjugate acid-base pair.
10) Which of the following pairs of acids and conjugate bases is incorrectly labeled?
Answer: B) HFO₂/HFO₃
Explanation:
- HFO₂ (fluorous acid) and HFO₃ are not a conjugate acid-base pair, as they don’t differ by just one proton. The correct pair should involve a proton transfer, such as HSO₄⁻ and SO₄²⁻.
These questions focus on understanding acid-base theories, particularly Arrhenius and Bronsted-Lowry concepts.