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Use the Data Booklet to help you answer this question Which is the main aspartic acid species present in an aqueous solution at pH = 14? [1 mark] - AQA - A-Level Chemistry - Question 35 - 2019 - Paper 3
Question 35
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Use the Data Booklet to help you answer this question Which is the main aspartic acid species present in an aqueous solution at pH = 14? [1 mark]
Worked Solution & Example Answer:Use the Data Booklet to help you answer this question Which is the main aspartic acid species present in an aqueous solution at pH = 14? [1 mark] - AQA - A-Level Chemistry - Question 35 - 2019 - Paper 3
Step 1
Identify the aspartic acid species present at pH = 14
Answer
At pH 14, aspartic acid (which has the formula H₂N-CH(COOH)-CH₂-COOH) will largely exist in its deprotonated forms due to the basic nature of the solution. The carboxylic acid groups (COOH) will lose protons to form carboxylate ions (COO⁻).
At this high pH, the amino group (NH₂) will also remain in its neutral form (NH₂), as it does not protonate under these conditions.
Thus, the main species of aspartic acid present at pH = 14 will be:
- One amino group: NH₂
- Two carboxylate groups: COO⁻
This corresponds to option D in the question.