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Solved: Citrus fruits are rich in citric acid, a compound
Chapter 2, Problem 65P(choose chapter or problem)
Citrus fruits are rich in citric acid, a compound with three \(\mathrm{COOH}\) groups. Explain the following:
a. The first \(p K_{a}\) (for the \(\mathrm{COOH}\) group in the center of the molecule) is lower than the pKa of acetic acid.
b. The third \(p K_{a}\) is greater than the \(p K_{a}\) of acetic acid.
Equation Transcription:
Text Transcription:
COOH
pK_a
Questions & Answers
QUESTION:
Citrus fruits are rich in citric acid, a compound with three \(\mathrm{COOH}\) groups. Explain the following:
a. The first \(p K_{a}\) (for the \(\mathrm{COOH}\) group in the center of the molecule) is lower than the pKa of acetic acid.
b. The third \(p K_{a}\) is greater than the \(p K_{a}\) of acetic acid.
Equation Transcription:
Text Transcription:
COOH
pK_a
ANSWER:
Solution 65P
Step 1 of 3:
Here, we are asked to explain the variation of pKa values for the given scenarios. Let’s first see what is a pKa.
pKa is an index that is used to express the strength of acids. It is the negative logarithm of the dissociation constant, Ka. Ka is an acid dissociation constant that is used to measure the strength of acidity.
We calculate the strength of acidity using the formula :
pKa = -log (Ka)
where, ‘p’ stands for ‘potential of’.
When Ka is calculated, usually the results are an extremely large number. Hence, for convenience, chemists simplified it to a smaller number, called pKa. pKa is the negative logarithm of the dissociation constant, Ka.
The smaller the pKa value, stronger is the acid, and the higher the pKa value, weaker is the acid. Inversely, the smaller the Ka value, weaker is the acid, and the higher the Ka value, stronger is the acid.