Unit 13 Acids & Bases

Acids and bases are among the most common substances in nature. Amino acids are the building blocks of proteins. The pH of rivers, lakes, and oceans is affected by dissolved acids and bases. Bodily functions depend on acids and bases.

Acids or bases that ionize extensively and are referred to as strong acids or bases. Acids or bases that do not ionize extensively are referred to as weak acids or bases.

Arrhenius Acids Restricted to aqueous solutions. ______________ – when dissolved in water, the concentration of H+ is increased. HCl  H+ + Cl- ______________ – when dissolved in water, the concentration of OH- is increased. NaOH  Na+ + OH-

Bronsted – Lowry Acid & Base Basic concept involves the transferring of a proton, H+ ion, from one substance to another substance. H+ + H2O  H3O+ (______________) H+ and H3O+ are used interchangeably

Acid – substance that can transfer a proton to another substance – ______________. Base – substance that can accept a proton – ______________

H2O Kw – ion product constant for water 1.0 x 10-14 Kw = [H3O+] [OH-] = 1.0 x 10-14 or [H+] [H+] = [OH-]  neutral solution [H+] > [OH-]  acidic solution [H+] < [OH-]  basic solution

If the [H+] = 2 x 10-5 M in a solution, is the solution acidic or basic? If the [OH-] = 3 x 10-9 M in a solution, is the solution acidic or basic? If the [OH-] = 1.0 x 10-7 in a solution, is the solution acidic or basic?

pH Scale The concentration of ______________in an aqueous solution is usually small. Concentration of H+ is expressed in terms of pH pH = -log [H+] The scale ranges from 0 – 14 0 – very acidic 14 – very basic

As [H+] increases, the pH ______________As [H+] decreases, the pH ______________

pOH Expresses the concentration of OH- pOH = -log [OH-]

pH + pOH = 14

Acid-Base Indicators Used to measure pH pH meters measure pH as well

A sample of freshly pressed apple juice has a pH of 3. 76 A sample of freshly pressed apple juice has a pH of 3.76. Calculate [H+]. A solution formed by dissolving an antacid tablet has a pH of 9.18. Calculate [H+].

In a sample of lemon juice, [H+] is 3.8 x 10-4 M. What is the pH? A commonly available window cleaning solution has a [H+] of 5.3 x 10-9 M. What is the pOH?