• Bronsted-Lowry definition of Acids and Bases

• Ionization constants of acids and bases

• The pH scale

• Solving equilibrium problems involving acids and bases

• Acid-base reactions of salts

• Acid strength and molecular structure

• Lewis Acids and Bases

Tro Chapter 15 - Acids and Bases

Suggested eoc problems for chapter 15: 33, 35, 47, 49, 51, 59, 65, 83, 85, 95, 97, 103, 107, 117

Classical or Arrhenius Definition of Acids and Bases •  Acids have H in their formula and dissociate in water to yield H+

•  Bases have OH in their formula and dissociate in water to yield OH-

Tro 15.3 Bronsted-Lowry Definition of Acids and Bases

• Acids are hydrogen ion (H+) donors

• Bases are hydrogen ion (H+) acceptors

Tro 15.4 Strong Acids – Completely Dissociate!

Tro 15.4 Weak Acids – Do not dissociate completely! Autoionization of water: Kw = 1 x 10-14 Tro 15.5

Kw = [H3O+][OH-] = 1 x 10-14

The pH and pOH Scales: A way to quantify Acidity and Basicity

The pH scale and some common substances

Solving equilibrium problems for A/B reactions

Phenylacetic acid (C6H5CH2COOH) - HPAc builds up in the blood of persons with phenylketonuria, an inherited disorder that if untreated, causes mental retardation and death. A study of the acid shows that the pH of 0.12 M HPAc is 2.60. What is the Ka of phenylacetic acid?

Tro 15.6 and 15.7 Propanoic acid (CH3CH2COOH) - HPr - is an organic acid whose salt is used to retard mold growth in foods. What is the [H3O+] of 0.10 M HPr if Ka = 1.3 x 10-5?

Methylamine is a weak base. Find the pH of a 0.33 M solution of methylamine.

Acid-base properties of salt solutions

Consider the following salts and determine whether a solution would be acidic or basic if they were dissolved in water:

NH4Cl

Fe(NO3)3

CH3COONa

NaH2PO4

Tro 15.8

Polyprotic Acids Tro 15.9

Ascorbic acid (H2C6H6O6) - H2Asc - known as vitamin C, is a diprotic acid (Ka1 = 1.0 x 10-5, and Ka2 = 5.0 x 10-12). Calculate [H2Asc], [Hasc-] and [Asc2-] and the pH of 0.050 M H2Asc.

Polyprotic Acids cont’d

Lewis Acids and Lewis Bases

• Lewis acids are electron pair acceptors

(e.g. Fe3+, Ag+, Al3+)

• Lewis bases are electron pair donors

• (e.g. NH3, OH-, H2O)

Tro 15.11 Lewis Acid-Base Reactions

•  BF3 + HF ⇔ H+1BF4-1

F

B F

F

H F •• ••

•• +

F

B F

F

F -1

H+1

Acid Rain natural rain water has a pH of 5.6

CO2 + H2O H2CO3

Many natural and pollutant gases dissolved in the air are nonmetal oxides including CO2, SO2, NO2

Nonmetal oxides are acidic CO2 + H2O ⇔ H2CO3 2 SO2 + O2 + 2 H2O ⇔ 2 H2SO4

pH of rainwater in various parts of the USA and the effects of acid rain