This question was posted: At 22 °C an excess amount of a generic metal hydroxide M(OH)2, is mixed with pure water. The resulting equilibrium solution has a pH of 10.56. What is the Ksp of the compound at 22 °C?

Question

This question was posted: At 22 °C an excess amount of a generic metal hydroxide M(OH)2, is mixed with pure water. The resulting equilibrium solution has a pH of 10.56. What is the Ksp of the compound at 22 °C?

I have found my [OH-] concentration (3.63x10^-4)

but I am looking at it and cannot find how they got the concentration of [OH-]. Everything that needs to be done after that I understand. I just do not get how they got the concentration

Answer 1

Your post isn't entirely clear as to what you do and don't understand. Here is how you do it.

........M(OH)2 ==> M^2+ + 2OH^-
The problem tells you pH = 10.56 which makes pOH = 3.44 and from that
pOH = -log(OH^-) = 3.44
Therefore, (OH^-) = 3.63E-4

Ksp = (M^2+)(OH^-)^2 = ?
(M^2+) = 1/2 x 3.63E-4
(OH^-) = 3.63E-4
Ksp = about 2E-11

Answer 2

I was just having trouble with getting the [OH-] concentration. I had the answer just didn't know how to get to it. Thank you, it helped.

Answer 3

To determine the concentration of hydroxide ions ([OH-]) in the solution, we can use the pH value.

pH is a measure of the concentration of hydrogen ions ([H+]) in a solution. The pH scale ranges from 0 to 14, where a pH of 7 is considered neutral, pH less than 7 is acidic, and pH greater than 7 is basic or alkaline. The relationship between pH and [H+] is given by the equation pH = -log[H+].

In this case, the solution has a pH of 10.56, which means the concentration of hydrogen ions ([H+]) can be calculated as follows:

[H+] = 10^(-pH) (taking the antilog of pH)

[H+] = 10^(-10.56)

Calculating this value, we find that [H+] = 2.49 x 10^(-11) M.

Since water dissociates to form equal amounts of [H+] and [OH-], the concentration of hydroxide ions ([OH-]) will also be equal to 2.49 x 10^(-11) M.

It seems that you have found a different concentration of [OH-] (3.63x10^-4) based on the given information. It's possible that there might be an error in the calculations or a misunderstanding of the question. Double-check your calculations to make sure you haven't missed anything, or review the problem statement to make sure you have all the necessary information.