2 Definitions and Formulas The pH scale is defined as the negative log of the concentration of H+:pH = -log[H+]The pOH scale is defined as the negative log of the concentration of OH-, [OH-].pOH = -log[OH-]With this scale, calculating the pOH can be done in the same manner as the pH scale.pH + pOH = 14
3 ExamplesWhat is the pH of a solution that contains 25 g of hydrochloric acid (HCl) dissolved in 1.5 L of water?
4 Quiz Determine the pH of a .0034 M HNO3 solution. Determine the pOH of the solution in #1.What is the pH of a 2.4 x 10-5 M HCl solution?
5 Auto-Ionization of Water In water, Kc= [H+][OH-]55.5 M[OH-]= Kw [H30+]= Kw[H30+] [OH-]ion product constant for water Kc (55.5M) = [H+][OH-] = Kw Kw= [H30+] [OH-] Kw=Example: What is the hydroxide ion concentration in an aqueous solution that is 4.0 x 10-5 M H30+?[OH-] = (1.0 x 10-14)(4.0 x 10-5)=2.5 x M
6 PracticeWhat is the hydronium ion concentration in an aqueous solution containing 3.5 x 10-7 OH-?[H30+] = (1.0 x 10-14)(3.5 x 10-7)=2.9 x 10-8What is the hydroxide ion concentration in an aqueous solution containing 8.34 x H30+ ?[OH-] = (1.0 x 10-14)(8.34 x 10-12)=1.20 x 10 -3
7 Strong Acids dissociate completely in water to form hydronium ion(s) ExamplesHClHNO3H2SO4
8 Strong Bases dissociate completely in water to form hydroxide ions Examples:NaOHKOHCa(OH)2