1. Prentice-Hall Chapter 19.1 Dr. Yager
Acid-Base Theories
Prentice-Hall Chapter 19.1
Dr. Yager

2. Objectives Define the properties of acids and bases.
Compare and contrast acids and bases as defined by the theories of Arrhenius, BrØnsted-Lowry, and Lewis.

3. Properties of Acids
Acids taste sour, will change the color of an acid-base indicator, and can be strong or weak electrolytes in aqueous solution.
Citrus fruits contain citric acid Tea contains tannic acid.

4. Properties of a Base
Bases taste bitter, feel slippery, will change the color of an acid-base indicator, and can be strong or weak electrolytes in aqueous solution.
Antacids neutralize stomach acid. Ca(OH)2 is used in mortar.

5. Definitions of Acids and Bases
Arrhenius acid: hydrogen containing compound that increases hydronium ion concentration [H3O+] in an aqueous solution
Arrhenius base: compound that increases hydroxide ion concentration [OH-] in an aqueous solution
BrØnsted-Lowry acid: hydrogen ion (H+) donor
BrØnsted-Lowry base: hydrogen ion acceptor
Lewis acid/base: electron-pair acceptor/donor

6. Arrhenius Acids and Bases
Arrhenius acids are hydrogen-containing compounds that ionize to yield hydrogen ions (H+) in aqueous solution, thus also increasing hydronium ion concentration [H3O+]:
HCl (aq) + H2O(l)  H3O+ (aq) + Cl- (aq)
Arrhenius bases are compounds that ionize to yield hydroxide ions (OH–) in aqueous solution.
NaOH (aq)  Na+ (aq) + OH- (aq)
Most common understanding of acids and bases

7. Hydrochloric Acid

8. Arrhenius Acids
Acids that contain one ionizable hydrogen, such as nitric acid (HNO3), are called monoprotic acids.
Acids that contain two ionizable hydrogens, such as sulfuric acid (H2SO4), are called diprotic acids.
Acids that contain three ionizable hydrogens, such as phosphoric acid (H3PO4) are called triprotic acids.

10. Arrhenius Base
Hydroxide ions are one of the products of the dissolution of an alkali metal in water.

11. Arrhenius Base

12. Milk of magnesia is a base used as an antacid.

13. Brønsted-Lowry Acids and Bases
The Brønsted-Lowry theory defines an acid as a hydrogen-ion donor, and a base as a hydrogen-ion acceptor.

14. Why Ammonia is a Base

15. Conjugate Acids and Bases
A conjugate acid is the particle formed when a base gains a hydrogen ion.
A conjugate base is the particle that remains when an acid has donated a hydrogen ion.

16. Conjugate Acids and Bases
A conjugate acid-base pair consists of two substances related by the loss or gain of a single hydrogen ion.
A substance that can act as both an acid and a base is said to be amphoteric.

18. Why H2SO4 is an Acid
A water molecule that accepts a hydrogen ion becomes a positively charged hydronium ion (H3O+) and the H2SO4 gives up a hydrogen ion and becomes a negatively charged hydrogen sulfate ion (HSO4-).

19. Lewis Acids and Bases
Lewis proposed that an acid accepts a pair of electrons during a reaction, while a base donates a pair of electrons.

20. Lewis Acids and Bases
A Lewis acid is a substance that can accept a pair of electrons to form a covalent bond.
A Lewis base is a substance that can donate a pair of electrons to form a covalent bond.

23. a. H2O is donating the electrons and H+ is accepting the electrons
b. AlCl3 is accepting the electrons and Cl- is donating the electrons

24. Theories in Order of Discovery

25. 1. Which of the following is NOT a characteristic of acids?
taste sour
are electrolytes
feel slippery
affect the color of indicators

26. 1. Which of the following is NOT a characteristic of acids?
taste sour
are electrolytes
feel slippery
affect the color of indicators

27. 2. Which compound is most likely to act as an Arrhenius acid?
H2O
NH3
NaOH
H2SO4

28. 2. Which compound is most likely to act as an Arrhenius acid?
H2O
NH3
NaOH
H2SO4

29. 3. A Lewis acid is any substance that can accept
a hydronium ion.
a proton.
hydrogen.
a pair of electrons.

30. 3. A Lewis acid is any substance that can accept
a hydronium ion.
a proton.
hydrogen.
a pair of electrons.