1. General Characteristics
Acids and Bases
General Characteristics

2. Originally, chemists classified substances as acids or bases based on properties that were easily observed without the advanced lab equipment of today
They did this using aqueous solutions of the compounds in question

3. Common Characteristics of Acids
In aqueous solution
have a sour taste
react with bases to produce salts and water (next lesson)
change the color of acid/base indicators
react with metals to produce hydrogen gas
conduct electric current

4. Common Characteristics of Bases
In aqueous solution. . .
have a bitter taste
change the color of acid/base indicators
feel slippery
react with acids to produce salt and water (next lesson)
conduct electric current

5. Binary Acid nomenclature
a binary acid contains two different elements- one of which is hydrogen
hydro + root of second element + ic
example: HCl
hydro + chlor + ic = hydrochloric
try naming HF on your own

6. Oxoacid Nomenclature Oxoacids: contain oxygen in addition to Hydrogen
If the oxyacid contains more than one O, use the following rules.
addition of one O atom to “-ic” acid: name “per…-ic” acid
Ex. HClO3 = chloric acid
HClO4 = perchloric acid
removal of one O atom from “-ic” acid: name “-ous” acid
-Ex. HClO2 = chlorous acid
removal of 2 O atoms from “-ic” acid: name “hypo…-ous” acid
-Ex. HClO = hypochlorous acid

7. As we mentioned before, acids and bases conduct electricity in solution, so they must ionize
example
HCl  H+ + Cl-

8. Definition of Acids and Bases
Svante Arrhenius defined acids and bases as
acid: substance that ionizes in water and increases the number of hydrogen ions
base: substance that ionizes in water and increases the number of hydroxide ions (OH-)

9. Hydrogen ions don’t last very long in water
they react immediately with water to form hydronium ions
H+ + H2O  H3O+

10. Acid Strength Strong acids ionize completely in water
they are completely soluble
Weak acids do not ionize completely in water
they are only partially soluble
Refer to table on page 501 (Blue Book)
page 483 (Red Book)

11. Bases
bases can increase hydroxide ion concentration in two different ways
ionization to form OH- ions
NaOH  Na+ + OH-
reaction with water to make OH-
NH3 + H2O  NH4+ + OH-
Base strength- refer to table on page 501 (Blue)
page 483 (Red)

12. 2. Bronsted-Lowery Definition
Second conceptual definition
Designed separately by two different scientists
Look at the H atom and the H+ ion e- e-
H+ is actually just a proton p+ p+ H H+
a. Acids
- a Bronsted-Lowery acid is a compound which releases a proton H+ H+ H+ H+ -
HCl + H2O 
H3O+ + Cl- H Cl
H3O+
H2O
HCl gives a proton to H2O, HCl is an acid
proton donor

13. b. Base
A Bronsted – Lowery base is a compound which accepts a proton H+ H+ H+ H+ -
HCl + H2O 
H3O+ + Cl- H Cl
H3O+
H2O
H2O accepts a proton. It is a base by B/L standards
proton acceptor
Examples – For each of the reactants, list the Bronsted Lowery acid and base
1. H3O+ + OH-  2 H2O
2. Cl- + H3O+  HCl + H2O
3. NH3 + H2O  NH OH-
acid
base
base
acid
base
acid

14. c. Amphiprotic/Amphoteric substances HCl + H2O  H3O+ + Cl-
Water is a base
NH3 + H2O  NH OH
Water is an acid
Water is both an acid and a base
Amphiprotic/Amphoteric substances
Can be either an acid or a base under different conditions
Will appear on both sides of chart L
d. Conjugate Acid/Base pairs
Many acid/base reactions are reversible
HCl + H2O
H3O+ + Cl-
acid
base
HCl + H2O
H3O+ + Cl-
acid
base
HCl + H2O
H3O+ + Cl-
When HCl becomes Cl-, it can now act as a base
HCl is an acid
Cl- is a base

15. Conjugate Acid/Base Pairs Acid and base differ only by one proton Acid
Has extra proton
Base
Missing a proton
base
acid
acid
base
NH3 + H2O NH4+ + OH-
Example
1. Indicate the conjugate acid/base pairs of the following
H2O + HNO H3O NO3-
CO H2O OH-+ HCO3-
base
base
acid
acid
base
acid
base
acid

16. C. Strength of Conjugate Acid/Base Pairs
If the acid is strong, its conjugate base is weak, and vice versa
HCl + H2O
H3O+ + Cl-
Strong acid
Strong base
Weak base
Weak acid
Strong acid
Strength of Acids chart - acids side
The higher acid is the stronger one
Bases side
The LOWER base is the stronger one
Acids
HCl and HSO4-
HCl is stronger acid
Bases
HS- and HCO3-
HS- is stronger base
Example - Label each as either a stronger acid or base
HNO3 + HS H2S + NO3-
Strong base
strong
strong
weak
weak
acid
base
acid
base