Unit 8 Practice: Easy
Acids and Bases · 20 questions. Try each question before revealing the answer and worked explanation.
Question 1
What is a Brønsted-Lowry acid?
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Answer: A proton donor
Explanation: A Brønsted-Lowry acid gives an H⁺ to another species.
Question 2
What is a Brønsted-Lowry base?
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Answer: A proton acceptor
Explanation: A base accepts H⁺ from another substance.
Question 3
What is the conjugate base of HCl?
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Answer: Cl⁻
Explanation: When HCl loses H⁺:
HCl → H⁺ + Cl⁻
Cl⁻ is its conjugate base.
Question 4
What is the conjugate acid of NH₃?
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Answer: NH₄⁺
Explanation: NH₃ accepts H⁺:
NH₃ + H⁺ → NH₄⁺
Question 5
What does amphiprotic mean?
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Answer: A species can act as either an acid or a base.
Explanation: For example, H₂O can:
donate H⁺ and become OH⁻
accept H⁺ and become H₃O⁺
Question 6
Write the autoionization equation for water.
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Answer:
2H₂O ⇌ H₃O⁺ + OH⁻
Explanation: One water molecule transfers a proton to another.
Question 7
What is Kw at 25°C?
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Answer:
Kw = 1.0 × 10⁻¹⁴
Explanation:
At 25°C:
Kw = [H₃O⁺][OH⁻]
Question 8
In neutral water at 25°C, what is [H₃O⁺]?
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Answer: 1.0 × 10⁻⁷ M
Explanation: Neutral water has:
[H₃O⁺] = [OH⁻]
and their product equals 1.0 × 10⁻¹⁴.
Question 9
What is the pH of neutral water at 25°C?
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Answer: 7.00
Explanation:
pH = −log[H₃O⁺]
= −log(1.0 × 10⁻⁷)
= 7.00
Question 10
Write the pH equation.
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Answer:
pH = −log[H₃O⁺]
Question 11
Write the pOH equation.
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Answer:
pOH = −log[OH⁻]
Question 12
What is the relationship between pH and pOH at 25°C?
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Answer:
pH + pOH = 14.00
Question 13
A solution has [H₃O⁺] = 1.0 × 10⁻³ M. What is its pH?
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Answer: 3.00
Work:
pH = −log(1.0 × 10⁻³)
= 3.00
Question 14
A solution has [OH⁻] = 1.0 × 10⁻⁴ M. What is its pOH?
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Answer: 4.00
Explanation:
pOH = −log(1.0 × 10⁻⁴) = 4.00
Question 15
If pOH = 4.00 at 25°C, what is pH?
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Answer: 10.00
Work:
pH = 14.00 − 4.00
= 10.00
Question 16
What is a strong acid?
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Answer: An acid that ionizes essentially completely in water.
Explanation: Strong does not mean concentrated.
“Strong” describes degree of ionization.
Question 17
What is a weak acid?
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Answer: An acid that only partially ionizes in water.
Explanation: Weak acids establish an equilibrium rather than completely dissociating.
Question 18
Name three common strong acids.
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Answer: Examples include:
HCl, HBr, HNO₃
Explanation: Other commonly recognized strong acids include HI and HClO₄. The first proton of H₂SO₄ is also treated as strong.
Question 19
What does a large Ka mean?
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Answer: The acid is relatively strong.
Explanation: A large Ka means equilibrium favors ionized products more strongly.
Question 20
What does a small pKa generally mean?
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Answer: A stronger acid
Explanation:
pKa = −log Ka
So a larger Ka gives a smaller pKa.