The pH of a solution is 1.3, what is the hydroxide ion concentration?

To find the hydroxide ion concentration, we first need to calculate the hydrogen ion concentration using the formula:

pH = -log[H+]

Given that the pH is 1.3, we can use the formula to find the hydrogen ion concentration:

1.3 = -log[H+]

-1.3 = log[H+]

[H+] = 10^-1.3
[H+] = 0.0501 M

Since water dissociates into equal parts of hydrogen ions and hydroxide ions, the hydroxide ion concentration will also be 0.0501 M.