pH And pOH

Water Water autoionizes H 2 O + H 2 O H 3 O+ + OH- Hydrogen ion concentration determines the acidity of the solution Kc = [H3O+][OH-] ionization constant

Ion-product Constant Kc = [H3O+][OH-] could be written as Kc = [H+][OH-] To indicate this is for water, we write it as Kw Kw is the ion product constant, the product of the concentration of H+ and OH- at a particular temperature In pure water at 25 o C, Kw = 1.0 x

Example 1 Concentrations of OH- in household ammonia is M. Calculate the concentration of H+ ions. Kw = [H+][OH-] so [H+] = Kw/[OH-] [H+] = 1.0 x / = 4.0 x M Since [H+]<1.0 x M, this is basic

pH and pOH pH measures [H+]: pH = -log[H+] pOH measures [OH-]: pOH = -log[OH-] pH + pOH = 14.00

Example 2 What is the pH of a 1.0 x M NaOH solution? NaOH → Na+ + OH- so 1.0 x M NaOH produces 1.0 x M [OH-] Kw = [H+][OH-] [H+] = Kw/[OH-] = (1.0 x )/(1.0 x ) [H+]=1.0 x M pH = - log (1.0 x ) = 11

Example 3 Determine the hydronium ion concentration of an aqueous solution with pH 4.0 pH=-log [H+] [H+] = antilog -pH [H+] = antilog -4.0 [H+]=1.0 x 10 -4

Example 4 Determine the hydronium ion concentration of an aqueous solution with pH 4.0 pH=-log [H+] [H+] = antilog -pH [H+] = antilog -4.0 [H+]=1.0 x 10 -4