Final answer:
To find the concentration of hydrogen ions [H+] given the hydroxide ion concentration [OH-] and Kw, use the equation Kw = [H+][OH-] = 1.0 × 10^-14, then rearrange and solve for [H+].
Step-by-step explanation:
To find the concentration of hydrogen ions [H+] when you have the concentration of hydroxide ions [OH-] and the ion-product constant for water (Kw), you can use the equation:
Kw = [H+][OH-] = 1.0 × 10^-14 (at 25 °C)
Rearrange the equation to solve for [H+]:
[H+] = Kw / [OH-]
Then substitute the given values for Kw and [OH-] to calculate [H+].
For example, if [OH-] is 1.0 × 10^-10 M:
[H+] = (1.0 × 10^-14) / (1.0 × 10^-10)
[H+] = 1.0 × 10^-4 M
This calculation shows that as the concentration of OH- increases, the concentration of H+ must decrease to maintain the constant value of Kw.