What is the best buffer at ph = 5.0? justify your answer.
a) formic acid (pka = 3.8)
b) acetic acid (pka = 4.76)
c) ethylamine (pka = 9.0)

b) acetic acid (pKa = 4.76)

Explanation:

Considering the Henderson- Hasselbalch equation for the calculation of the pH of the buffer solution as:

pH=pKa+log[base]/[acid]

The weak acid for making the buffer must have a pKa value near to the desired pH of the weak acid.

So, near to value, pH = 5, acetic acid is close which have of pKa of 4.76

Thus, option B is correct.

"record the time to complete a chemical reaction" would most likely be part of a lab procedure.

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