A solution is found to contain 1 x 10-4 OH− ions, determine the pH of this solution.

I did this problem and got 4 but it is not going in as correct.

-log(1*10^-4)=4

It is; however, your calculation gives you pOH. If you want pH, use

pH + pOH = pKw = 14 and solve for pH.

Or you can use (H^+)(OH^-) = Kw = 1E-14

pH = -log(H^+)
pOH = - log(OH^-)

I did it and got 10 and it is saying that its incorrect

pOH = 4

pH = 10

Or
(H^+) = 1E-14/1E-4 = 1E-10
pH = 10
The data base is wrong or you posted the problem incorrectly. The pH is 10 for the above problem.

To determine the pH of a solution, you need to find the negative logarithm (base 10) of the concentration of hydrogen ions, denoted as [H+]. In this case, you were given the concentration of hydroxide ions, denoted as [OH-]. Remember that the concentrations of [H+] and [OH-] in water are related by the Kw constant, which is 1 x 10^-14 at 25°C.

To find [H+], you can use the fact that [H+][OH-] = Kw. Since [OH-] = 1 x 10^-4, you can substitute it into the equation and solve for [H+]:

[H+][OH-] = Kw
[H+](1 x 10^-4) = 1 x 10^-14
[H+] = (1 x 10^-14)/(1 x 10^-4)
[H+] = 1 x 10^-10

Now that you have the concentration of [H+], you can find the pH by taking the negative logarithm (base 10) of [H+]:

pH = -log([H+])
pH = -log(1 x 10^-10)
pH = -(-10)
pH = 10

Therefore, the pH of the solution is 10.