Shown here are the basic tools one needs to be able to calculate hydronium ion, hydroxide ion, pH, pOH, Ka, and Kb. when dealing with acid/base problems. I call it my “toolbox” and hope you find it useful!
[H3O+][OH¯] = Kw = 1.0 x 10-14 pX = -logX KaKb = Kw
All the ways you can find [H3O+] and [OH¯]:
All the ways you can find pH and pOH:
pH + pOH = 14 pH = 14 – pOH pOH = 14 – pH
pH = -log[[H3O+] pOH = -log[OH¯]
KaKb = Kw is used in hydrolysis problems. Use it to calculate the Kb of the conjugate base of a weak acid, or conversely, the Ka of the conjugate acid of a weak base:
In general, pX is a power function, and it means you take the negative logarithm of the variable or number, hence, pX = -logX.