Which structure is formed by aspartic acid in solution at pH 12?
A
H₂N—CH—COO⁻
|
COOH
B
H₂N—CH—COOH
|
COOH
C
H₂N—CH—COO⁻
|
COO⁻
D
H₂N—CH—COOH
|
COO⁻ - AQA - A-Level Chemistry - Question 15 - 2018 - Paper 3
Question 15
Which structure is formed by aspartic acid in solution at pH 12?
A
H₂N—CH—COO⁻
|
COOH
B
H₂N—CH—COOH
|
COOH
C
H₂N—CH—COO⁻
... show full transcript
Worked Solution & Example Answer:Which structure is formed by aspartic acid in solution at pH 12?
A
H₂N—CH—COO⁻
|
COOH
B
H₂N—CH—COOH
|
COOH
C
H₂N—CH—COO⁻
|
COO⁻
D
H₂N—CH—COOH
|
COO⁻ - AQA - A-Level Chemistry - Question 15 - 2018 - Paper 3
Step 1
Identify the relevant pH conditions
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Answer
At pH 12, aspartic acid would predominantly exist in its deprotonated form, where the carboxylic acid groups lose protons (H⁺) and are negatively charged.
Step 2
Analyze the given structures
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Answer
Examine each option (A, B, C, D) to determine which one reflects deprotonation of the carboxylic acid groups at pH 12.
Step 3
Select the correct structure
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Answer
The correct structure is D, as it shows the amine group (H₂N) and has both carboxylic acid groups as COO⁻, which is consistent with the condition at pH 12.
