1. Acid-Base Reactions
Section 14.3

2. Conjugate Base
Conjugate base: the species that remains after a Brønsted-Lowry acid has given up a proton
Acid conjugate base

3. Conjugate Acid
Conjugate acid: the species that is formed when a Brønsted-Lowry base gains a proton
base conjugate acid

4. Acid-Base Reactions
Usually acid-base reactions are equilibrium systems
The forward and reverse reactions occur
They involve conjugate acid-base pairs
CH3COOH(aq) + H2O(l) H3O+(aq) + CH3COO - (aq)acid base conjugate conjugate acid base
Do activity with acid base reactions here: write various reactions on the board and have students label them with cards that have acid, base, conjugate acid and conjugate base on them

5. Strength of Conjugate Acids and Bases
The stronger an acid is, the weaker its conjugate base
The stronger a base is, the weaker its conjugate acid

7. Amphoteric Compounds
Amphoteric: any species that can react as either an acid or a base
Example: H2O can act as either an acid or a base
H2SO4(aq) + H2O(l) H3O+(aq) + HSO4-(aq)
NH3(g) + H2O(l) NH+4(aq) + OH-(aq)

8. Continued
The amphoteric substance acts as either an acid or a base depending on the strength of the acid or base with which it is reacting

9. Neutralization Reactions
A strong acid and a strong base react to form a salt and water
Aqueous HCl completely dissociates in water to form H3O+ and Cl-
Aqueous NaOH completely dissociates in water to form Na+ and OH-

10. Strong Acid + Strong Base
NaOH(aq) + HCl(aq)  NaCl(aq) and H2O(l)

11. Vocabulary
Neutralization: (in aqueous solutions) the reaction of hydronium ions and hydroxide ions to form water molecules
Salt: an ionic compound composed of a cation from a base and an anion from an acid

12. Acid Rain
Pure rain water is slightly acidic because of dissolved carbon dioxide that forms carbonic acid with a pH = 5.6
Acid rain is defined as rain with a pH < 5.6
Other acids cause rain to have a lower pH

13. More about Acid Rain
Main “evil” acids in rain are sulfuric acid and nitric acid
Caused by the reaction of oxides of sulfur and oxides of nitrogen
Can be deposited in rain water, fog, or snow
Drastically affects lakes, streams, ponds and soil