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A 0.10 mol dm⁻³ aqueous solution of an acid is added slowly to 25 cm³ of a 0.10 mol dm⁻³ aqueous solution of a base - AQA - A-Level Chemistry - Question 14 - 2020 - Paper 3
Question 14
A 0.10 mol dm⁻³ aqueous solution of an acid is added slowly to 25 cm³ of a 0.10 mol dm⁻³ aqueous solution of a base. Which acid–base pair has the highest pH at the ... show full transcript
Worked Solution & Example Answer:A 0.10 mol dm⁻³ aqueous solution of an acid is added slowly to 25 cm³ of a 0.10 mol dm⁻³ aqueous solution of a base - AQA - A-Level Chemistry - Question 14 - 2020 - Paper 3
Step 1
Which acid–base pair has the highest pH at the equivalence point?
Answer
To determine which acid-base pair has the highest pH at the equivalence point, we should analyze the nature of the acids and bases involved:
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Understanding the pH at equivalence: At the equivalence point, a strong acid with a strong base (e.g., HCl and NaOH) will produce a neutral solution with a pH of around 7. Conversely, a weak acid with a strong base (e.g., CH₃COOH and NaOH) will lead to a basic solution due to the presence of the conjugate base.
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Analyzing the options:
- Option A: CH₃COOH (weak acid) and NaOH (strong base) will yield a basic solution.
- Option B: CH₃COOH (weak acid) and NH₃ (weak base) will still result in a neutral or slightly acidic solution.
- Option C: HCl (strong acid) and NaOH (strong base) will yield a neutral solution at pH 7.
- Option D: HCl (strong acid) and NH₃ (weak base) will result in a solution that is more acidic than neutral.
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Conclusion: Among the given options, Option A (CH₃COOH and NaOH) will have the highest pH at the equivalence point because the ionic species present will result in a basic pH.