Question

Which of the following substances (along with its corresponding salt) would be best suited for generating a buffer solution with a pH below 7?

a. CH3CO2H
b. C5H5N
c. HCl
d. None of the above

Answer 1

CH3CO2H

Step-by-step explanation:

A weak acid, such as acetic acid, paired with its conjugate base (here, the acetate ion) will be an ideal system for creating an acidic buffer solution with a pH below 7.

Answer 2

d. None of the above

Step-by-step explanation:

A buffer works when pH of the buffer is ± 1. Out of this range, the buffering capacity is very low.

Acetic acid, CH₃CO₂H, has a pKa of 4.74. That means its buffering capacity is between 3.74 and 5.74 of pH. Is not a good buffer to pH 7

Pyridine is a weak base with pKa of 5.52. Its buffering capacity is between 6.52 and 4.52. Is not a good buffer to pH 7

HCl is a strong acid. Just weak acids and bases can produce a buffer with its conjugate base. HCl can't produce a buffer.

Thus, right answer is:

d. None of the above