Final answer:
The ratio of citric acid to monosodium citrate in a 1.0 M citric acid solution with a pH of 2.09 is 10:1, as determined by applying the Henderson-Hasselbalch equation.
Step-by-step explanation:
The student has asked about the ratio of citric acid to monosodium citrate in a 1.0 M citric acid solution with a pH of 2.09. To find this ratio, we can use the Henderson-Hasselbalch equation, which is:
pH = pKa + log([A-]/[HA]), where [A-] is the concentration of the base form (monosodium citrate) and [HA] is the concentration of the acid form (citric acid).
Using the equation:
2.09 = 3.09 + log([monosodium citrate]/[citric acid])
When we rearrange for log([monosodium citrate]/[citric acid]):
log([monosodium citrate]/[citric acid]) = 2.09 - 3.09
log([monosodium citrate]/[citric acid]) = -1
When we antilog both sides, we get:
[monosodium citrate]/[citric acid] = 10^(-1)
This means that the ratio of citric acid to monosodium citrate is 10:1, which corresponds to option b.