1. Introduction to Acids and Bases
2/24/2019
Reference: Khady Guiro

2. DO NOW Brainstorm What are common acids and bases?
What tools can be used to measure acids and bases?

3. Introduction
Organisms are often very sensitive to the effect of acids and bases in their environment.
They need to maintain a stable internal pH in order to survive—even in the event of environmental changes.
Many naturally occurring biological, geological, and man-made chemicals are capable of stabilizing the environment’s pH.
This may allow organisms to better survive in diverse environments found throughout the earth.

4. Introduction Cont.
Acids and bases are a way of classifying compounds based upon what happens to them when you place them in water.
An acid is a substance that yields an excess of hydrogen ions when dissolved in water.
A base is a substance that yields an excess of hydroxide ions when dissolved in water.

6. Definitions of Acids and Bases
An acid is a substance that breaks into ions in an aqueous solution.
A Base (is a substance that breaks into ions in an aqueous solution.
Note: aqueous solution is any solution where is the solvent.

7. ACIDS

8. Common Acids
Vinegar (acetic or ethanoic acid)
Citric Acid

9. Characteristics of Acids
Sour taste (for edible acids)
May burn your skin
Turn litmus paper from blue to red.

10. Other Examples of Acids
HCl Hydrochloric Acid
H2SO4 Sulfuric Acid
CH3COOH Acetic Acid (Vinegar)

11. BASES

12. Common Bases
Ammonia

13. Characteristics of Bases
Bitter taste (for edible bases only)
Can be poisonous and corrosive.
Feels slippery
Turn litmus from red to blue.

14. Other examples of Bases
Sodium Hydroxide NaOH
Potassium Hydroxide KOH
Ammonia NH3

15. Three Definitions of Acids and Bases

16. Three Definitions of Acids and Bases
Svante Arrhenius (Swedish 1887)
Bronsted- Lowry (Danish and English 1923 independently proposed definition)
Gilbert Lewis (American 1920’s)

17. Arrhenius: based on Theory Ionization of Acids and Bases
Acids produce hydrogen ions (H+) in an aqueous solution, while bases produce hydroxide ion (OH-).
Acid: HCl (aq) H+ (aq) + Cl- (aq)
Base: NaOH(aq) Na+(aq) + OH-(aq)

18. Bronsted- Lowry Definition of Acids and Bases
An acid is a proton (H+) donor.
A base is a proton (H+) acceptor.
Example:
HF + H2O H3O+ + F-
Acid Base
H3O+ : hydronium ion

19. Lewis Definition of Acids and Bases
An acid accepts a pair of electrons.
A base donates a pair of electrons.
This is a more general definition than the previous two.
Example:
:NH3 + H+  NH4+

20. Three Models of Acids and Bases
Definition of Acid
Definition of Base
Arrhenius
H+ producer
OH- producer
Bronsted-Lowry
H+ donor
H+ acceptor
Lewis
Electron-pair acceptor
Electron-pair donor

21. Binary acids
Binary acids are certain molecular compounds in which hydrogen is combined with a second nonmetallic element; these acids include HF, HCl, HBr, and HI. HCl, HBr, and HI are all strong acids, whereas HF is a weak acid

22. Ternary acids
3 types of ternary compounds: Ternary salts Ternary acids (Oxyacids) Ternary bases

23. Conjugate Acids and Bases
Conjugate acid is the particle formed that has received the proton. (ex: H3O+)
Conjugate base is the particle left from the acid once it has donated the proton.

24. Conjugate Acids and Bases
General expression:
HA (aq) + H2O (l) H3O+ (aq) + A- (aq)
Acid Base Conjugate Conjugate
Acid Base

25. Conjugate Acid-Base Pairs
conjugates
acid
base
NH H2O NH OH-
base
acid
conjugates
base acid CA CB
NH H2O NH OH-

26. Conjugate Acid-Base Pairs
conjugates
base2
acid2
HC2H3O H2O H3O C2H3O2OH-
acid1
base1
conjugates
acid base CA CB
HC2H3O H2O H3O C2H3O2OH-
The reaction proceeds in the direction such that the stronger acid
donates its proton to the stronger base.