The pH of a diet Coca Cola solution is 3.12. What is the concentration of [OH^-] present in this solution?

Question

Quizplus · Accepted Answer

The pH of the solution can be used to calculate the concentration of [H+]: 
pH = -log[H+]
3.12 = -log[H+]
[H+] = 8.63x10^-4 M

Since this is a Coca Cola solution, we can assume that there is negligible presence of other acidic or basic compounds. Therefore, the [OH-] concentration can be calculated using the Kw expression: 
Kw = [H+][OH-] = 1x10^-14
[OH-] = Kw/[H+]
[OH-] = 1.16x10^-11 M

Therefore, the concentration of [OHS-] can be calculated using the following equation: 
[OHS-] + [OH-] = [H2O]
[OHS-] = [H2O] - [OH-]
Assuming that the volume of the solution is 1 L, the concentration of water is approximately 55.6 M. 
[OHS-] = 55.6 M - 1.16x10^-11 M
[OHS-] = 55.6 M

However, since the [OHS-] concentration is much larger than the [OH-] concentration, we can assume that the [OHS-] concentration is equal to the total concentration of solutes in the solution. Therefore, the concentration of [OHS-] is approximately 55.6 M.

The correct answer is C: [OHS-] = 1.3x10^-11 M.

The PH of a Diet Coca Cola Solution Is 3