Buffer solutions Quiz
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5 questions, one answer each
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1. Which mixture is an acidic buffer?
- A. HCl and NaCl
- B. CH₃COOH and CH₃COONa
- C. NH₃ and NH₄Cl
- D. NaOH and NaCl
2. A buffer contains 0.20 mol dm⁻³ HA (Ka = 2.0 × 10⁻⁵ mol dm⁻³) and 0.10 mol dm⁻³ A⁻. What is [H⁺]?
- A. 1.0 × 10⁻⁵ mol dm⁻³
- B. 2.0 × 10⁻⁵ mol dm⁻³
- C. 4.0 × 10⁻⁵ mol dm⁻³
- D. 4.0 × 10⁻⁶ mol dm⁻³
3. In an NH₃/NH₄Cl buffer, which reaction removes added OH⁻?
- A. NH₃ + OH⁻ → NH₂⁻ + H₂O
- B. NH₄⁺ + OH⁻ → NH₃ + H₂O
- C. Cl⁻ + OH⁻ → HCl + O²⁻
- D. NH₃ + H⁺ → NH₄⁺
4. Why does the pH of a buffer change only slightly when a little acid is added?
- A. The ratio [HA]/[A⁻] changes only slightly
- B. The acid is completely neutralised so none remains
- C. Ka changes to compensate
- D. The water in the buffer absorbs the acid
5. A buffer is made from 0.0200 mol HA and 0.0400 mol A⁻ in 100 cm³ (Ka = 1.00 × 10⁻⁴ mol dm⁻³). What is its pH?
- A. 3.70
- B. 4.00
- C. 4.30
- D. 3.30