Final answer:
To calculate the pH of a solution with a known hydroxide ion concentration of 1.0 x 10^-5 M, find the concentration of hydrogen ions by dividing the ion-product constant of water (Kw) by the given hydroxide ion concentration, and then take the negative logarithm of the hydrogen ion concentration. The result is a pH of about 9, indicating the solution is basic.
Step-by-step explanation:
To find the pH of an aqueous solution with a hydroxide ion concentration ([OH-]) of 1.0 x 10^-5 M, we use the relationship between the concentration of hydroxide ions and hydrogen ions ([H+]) in water at 25°C, which is characterized by the ion-product constant of water (Kw = 1.0 x 10^-14). First, calculate the concentration of hydrogen ions by dividing Kw by the concentration of hydroxide ions:
Kw = [H+] × [OH-] ⇒ [H+] = Kw / [OH-] = 1.0 x 10^-14 / 1.0 x 10^-5 = 1.0 x 10^-9 M
Now, the pH can be determined by taking the negative logarithm of the hydrogen ion concentration:
pH = -log [H+] = -log (1.0 x 10^-9) ≈ 9
Since the pH is greater than 7, the solution is basic.