What is the OH- concentration of a solution that has H+ of 4.2 M?

Answer 1

First find the pH using the [H+]: pH = -log[H+] —> pH = -0.623

Then use the pH to find the pOH: pH + pOH = 14 —> -0.623 + pOH = 14 —> pOH = 14.623

Then calculate the [OH^-]: [OH^-] = 10^-pOH —> [OH^-] = 2.38 x 10^-15