Question

What is the ratio of citric acid (pK1=3.09) to monosodium citrate in a 1.0 M citric acid solution with a pH = 4.09?

a) 1:1
b) 10:1
c) 1:10
d) 100:1

Answer 1

The ratio of citric acid to monosodium citrate in a 1.0 M citric acid solution with a pH of 4.09 is 1:10, using the Henderson-Hasselbalch equation. This corresponds to option c) 1:10.

Step-by-step explanation:

To calculate the ratio of citric acid to monosodium citrate in a 1.0 M citric acid solution with a pH of 4.09, we need to use the Henderson-Hasselbalch equation:
`pH = pKa + log([A-]/[HA])`

Where:

• pH is the pH of the solution.
• pKa is the acid dissociation constant.
• [A-] is the concentration of the conjugate base (monosodium citrate).
• [HA] is the concentration of the acid (citric acid).

Plugging in the known values:

4.09 = 3.09 + log([A-]/[HA])

1 = log([A-]/[HA])

10^1 = [A-]/[HA]

[A-]/[HA] = 10

The ratio of citric acid to monosodium citrate is 1:10, which is option c.