Objectives◦Define Brønsted-Lowry acids and bases.◦Differentiate between Brønsted-Lowry and Arrhenius acids and bases.◦Identify conjugate acid-base pairs.◦Identify the proton transfer in Brønsted-Lowry acid-base reactions.

Chapter 15.1Acids and Bases

Arrhenius Acids and Bases

Arrhenius acid: any substance that

produces H3O+ when dissolved in water.

Arrhenius base: any substance that

produces OH- when dissolved in water.

Arrhenius acids and bases are limited to

aqueous solutions.

Brönsted-Lowry Acids and Bases

Brönsted-Lowry acid: proton (H+) donor

Brönsted-Lowry base: proton (H+)

acceptor

Brönsted-Lowry acid-base reactions

involve the transfer of a proton (H+) from

an acid to a base.

Brönsted-Lowry acids and bases are not

limited to aqueous solutions.

Conjugate Acid-Base Pairs

Conjugate acid-base pairs: molecules or

ions that differ by a single proton (H+).

The acid contains the proton (H+) that is

transferred to a molecule or ion.

The conjugate base is the molecule or ion

remaining after the loss of the proton (H+).

Conjugate Acid-Base Pairs

HF(aq) + H2O(l) ⇌ F-(aq) + H3O+(aq)

H+ is transferred from HF to H2O

acid conjugate base

base conjugate acid

Conjugate Acid-Base Pairs

Acid Base

HF F-

H2SO4 HSO4-

HSO4- SO4

2-

NH4+ NH3

H3O+ H2O

H2O OH-

H2O and HSO4- are amphoteric, acting as

both an acid and a base.

Brönsted-Lowry Acid-Base Reactions

acid + base ⇌ conj. base + conj. acid

HF + NH3 ⇌ F- + NH4+

HNO2 + H2O ⇌ NO2- + H3O

+

H2O + NH2- ⇌ OH- + NH3

In Class Example

Identify the acid-base conjugate pairs.

HCN(aq) + H2O(l) ⇌ H3O+(aq) + CN- (aq)

CH3NH2(aq) + H2O(l) ⇌ CH3NH3+(aq) + OH-(aq)

Objectives◦Relate hydrogen ion concentration to hydroxide ion concentration in aqueous solutions.◦Define pH and use it to express concentrations.◦Convert between concentrations of hydrogen ion and hydroxide ion, pH, and pOH. September 15th, 2016

Chapter 15.2Autoinoization of Water

Autoionization of Water

H2O(l) + H2O(l) ⇌ H3O+(aq) + OH-(aq)

H2O and H3O+ are a base-conjugate acid

pair.

H2O and OH- are an acid-conjugate base

pair.

Autoionization of Water

H2O(l) + H2O(l) ⇌ H3O+(aq) + OH-(aq)

Kw = [H3O+][OH-]

Kw is temperature dependent and is equal

to 1.0 x 10-14 at 25 oC.

Autoionization of Water

H2O(l) + H2O(l) ⇌ H3O+(aq) + OH-(aq)

In pure water, [H3O+] = [OH-]

Kw = [H3O+][OH-] = 1.0 x 10-14

[H3O+] = [OH-] = 1.0 x 10-7M

Calculating [H3O+] and [OH-] in non-pure water

Kw = 1.0x10-14 = [H3O+][OH-]

Adding an acid or a base to water changes

the concentration of both H3O+ and OH-

simultaneously.

Calculate the [OH-] in a solution with a

[H3O+] of 3.6 10-3 M.

pH Scale

pH stands for the negative log of the

hydronium ion concentration, -log10[H3O+]

• Calculate the pH of a solution that has a

0.0034 M [H3O+].

pH = -log(0.0034) = 2.47

pH units are always given to TWO decimal places.

Student Example

Calculate the pH of an aqueous solution

that has [OH-] = 7.7x10-7

pH and pOH Realtionship

[H3O+][OH-] = Kw = 1.0 10-14

pH + pOH = pKw = 14.0014

12

10

8

6

4

2

0

0

2

4

6

8

10

12

14

pH pOH

Acidic

Basic

Acidic Neutral Basic

pH <7 = 7 >7

pOH >7 = 7 <7

Objectives◦Define strong acids and bases.◦List the species that are strong acids and bases.◦Calculate the concentrations of species, the pH, and the pOH of solutions of strong acids and bases.

September 15th, 2016

Chapter 15.3Strong Acids and Bases

Strong Acids

HA(aq) + H2O (l) 100%

H3O+(aq) + A-(aq)

Strong acids ionize completely (100%) in

solution.

Strong Acids

There are six strong acids:

HCl hydrochloric acid

HBr hydrobromic acid

HI hydroiodic acid

HNO3 nitric acid

HClO4 perchloric acid

H2SO4 sulfuric acid

In Class Example

What is the pH of a 0.050 M HCl solution?

Strong Bases

Strong bases quantitatively produce

hydroxide ions in water.

Common strong bases include the group

IA and soluble IIA oxides and hydroxides.

NaOH(s) Na+(aq) + OH-(aq)

Li2O(s) + H2O(l) 2Li+(aq) + 2OH-(aq)

Student Example

Calculate the pH of a 0.035 M barium

hydroxide, Ba(OH)2, solution.

Student Example

Calculate the concentration of a HCl

solution having a pH of 3.75.

Calculate the concentration of a KOH

solution having a pH of 11.60.