Calculating Concentration

Acid-Base Properties of Water H2O + H2O H3O+ + OH- acid conjugate base base conjugate acid autoionization of water H2O (l) H+ (aq) + OH- (aq)

The Ion Product of Water H2O (l) H+ (aq) + OH- (aq) Keq = Kw = [H+][OH-] The ion-product constant (Kw) is the product of the molar concentrations of H+ and OH- ions at a particular temperature. At 250C Kw = [H+][OH-] = 1.0 x 10-14

Acid-Base Solutions Solution Is [H+] = [OH-] neutral [H+] > [OH-] acidic [H+] < [OH-] basic

Example 1 The concentration of H+ ions in an aqueous solution is 1.0×1 0 −5 M. Calculate the concentration of OH − ions? Is the solution acidic, basic, or neutral?

Example 2 Calculate the concentration of OH − ions in a HCl solution whose hydrogen ion concentration is 1.3 M.

pH pH = -log [H+] [H+] = 10−pH [OH-] = 10−pOH pH + pOH = 14.00 pOH = -log [OH+] [H+] = [OH-] [H+] > [OH-] [H+] < [OH-] Solution Is neutral acidic basic [H+] = 1.0 x 10-7 [H+] > 1.0 x 10-7 [H+] < 1.0 x 10-7 pH = 7 pH < 7 pH > 7 At 250C [H+] pH

Example 1 What is the pH, pOH, and hydroxide ion concentration of a solution with a hydrogen ion concentration of 1.0×1 0 −6 M?

Example 2 What is the pH, pOH, and hydrogen ion concentration of a solution if the concentration of the hydroxide ions is 9.6×1 0 −4 M?