Acid–Base Properties of Salts: Quiz
Seven questions on predicting the pH of salt solutions, Ka × Kb = Kw and salt-solution pH calculations, with explanations.
Acid–Base Properties of Salts: Quiz
7 questions
CO₃²⁻ is the conjugate base of a weak acid, so it takes protons from water and forms OH⁻. K⁺ is neutral.
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Answer: K₂CO₃
CO₃²⁻ is the conjugate base of a weak acid, so it takes protons from water and forms OH⁻. K⁺ is neutral.
NH₄⁺ is the conjugate acid of the weak base NH₃ and donates a proton to water. Cl⁻ is neutral.
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Answer: NH₄Cl
NH₄⁺ is the conjugate acid of the weak base NH₃ and donates a proton to water. Cl⁻ is neutral.
Both ions come from a strong base and a strong acid, so they are far too weak to react with water.
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Answer: Neither Na⁺ nor Cl⁻ reacts with water to change [H⁺] or [OH⁻]
Both ions come from a strong base and a strong acid, so they are far too weak to react with water.
Kb = Kw ÷ Ka = 1.0 × 10⁻¹⁴ ÷ 4.9 × 10⁻¹⁰ = 2.0 × 10⁻⁵. A very weak acid has a fairly strong conjugate base.
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Answer: 2.0 × 10⁻⁵
Kb = Kw ÷ Ka = 1.0 × 10⁻¹⁴ ÷ 4.9 × 10⁻¹⁰ = 2.0 × 10⁻⁵. A very weak acid has a fairly strong conjugate base.
[OH⁻] ≈ √(2.0 × 10⁻⁵ × 0.10) = 1.41 × 10⁻³ mol/L, pOH = 2.85, pH = 14.00 − 2.85 = 11.15. 2.85 is the pOH.
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Answer: 11.15
[OH⁻] ≈ √(2.0 × 10⁻⁵ × 0.10) = 1.41 × 10⁻³ mol/L, pOH = 2.85, pH = 14.00 − 2.85 = 11.15. 2.85 is the pOH.
At equivalence the solution contains sodium ethanoate, a basic salt, so the pH is above 7 (about 8.7 for 0.050 mol/L).
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Answer: 9
At equivalence the solution contains sodium ethanoate, a basic salt, so the pH is above 7 (about 8.7 for 0.050 mol/L).
NH₄Cl is acidic; NaCl is neutral; CH₃COO⁻ (Kb 5.6 × 10⁻¹⁰) is a weaker base than CN⁻ (Kb 2.0 × 10⁻⁵), so NaCN has the highest pH.
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Answer: NH₄Cl, NaCl, CH₃COONa, NaCN
NH₄Cl is acidic; NaCl is neutral; CH₃COO⁻ (Kb 5.6 × 10⁻¹⁰) is a weaker base than CN⁻ (Kb 2.0 × 10⁻⁵), so NaCN has the highest pH.