To find the pH of a solution given its hydroxide ion concentration, we can use the formula:
pH = -log [H+]
where [H+] is the concentration of hydrogen ions in moles per liter. However, we are given the concentration of hydroxide ions, [OH-], so we need to use the relationship between [H+] and [OH-] to find [H+]:
Kw = [H+][OH-]
where Kw is the ion product constant for water, which is equal to 1.0 x 10^-14 at 25°C. Solving for [H+], we get:
[H+] = Kw / [OH-]
[H+] = (1.0 x 10^-14) / (5.3 x 10^-8)
[H+] = 1.89 x 10^-7 M
Now we can find the pH:
pH = -log [H+]
pH = -log (1.89 x 10^-7)
pH = 6.72
Since the pH is greater than 7, the solution is basic.