What is the equation to find pH and pOH?

1 Answer
Jun 2, 2016

pH + pOH = 14

Explanation:

2H_2O rightleftharpoons H_3O^+ + OH^-

The auto-ionization constant of water is given by:

K_W = [ H_3O^+] [ OH^-]

Apply the log function to both sides of the equation:

log(K_W )=log( [ H_3O^+] [ OH^-])

log(K_W )= log[ H_3O^+] + log[ OH^-]

Multiply both sides of the equation by a negative sign

-{log(K_W )}= -{\ log[ H_3O^+] + log[ OH^-]\ }

-log(K_W )= -log[ H_3O^+] - log[ OH^-]

-log(1.0xx10^-14)= -log[ H_3O^+] - log[ OH^-]

14 = -log[ H_3O^+] - log[ OH^-]

pH = -log[ H_3O^+] " and " pOH= - log[ OH^-]

14 = pH + pOH =>

pH + pOH = 14