CHEM 121
Chapter 9
Winter 2014
1

produce H + ions
•
•
•
Naming:
:
For polyatomic ion acids:
Acids
HCl (g)  H 
2

Bases
Bases: donate OH ions
NaOH (s)  H 
•
•
•
3

Acids & Bases
• Brønsted-Lowry Acids:
HCl + H
2
O 
• Brønsted-Lowry Bases:
N H
3
+ H
2
O 
Conjugate acid-base pairs:
H A + B
4

3-minute Practice
What is conjugate acid of I-?
What is the conjugate base of CH
3
COOH?
5

Strong Acids & Bases
6

Weak Acids & Bases
•
•
H
2
O + NH
3
+
Reaction will favor side with weaker acid
7

Dissociation Constants
• Equilibrium constants for weak acids and bases
HA (aq) + H
2
O (l) +
•

H
3
O

 
 
H O

2
A
8

Dissociation of Water
Water is ______________
H
2
O (l) + pure water: [H
3
O + ] =
K w
=
9

3-minute Practice
Calculate the concentration of hydroxide ions in coffee, an aqueous solution containing 1.0 x 10 -5 M H
3
O + ions
Calculate the concentration of hydroxide ions in milk, which contains 5.0 x 10 -7 M H
3
O + ions
10

The pH Scale
Scale from ________
• Acidic
• Neutral
• Basic
Milk: [H
3
O + ] = 5.0 x 10 -7 M pH of milk =
11

3-minute Practice
Calculate the pH of a solution that has…
• [H
3
O + ] = 1.0 x 10 -8 M
• [OH-] = 4.0 x 10 -2 M
12

• Reactants:
• Products:
Example:
Neutralization
Molecular equation:
HCl (aq) + NaOH (aq) 
Net ionic equation:
13

Other Acid Reactions carbonates bicarbonates
•
•
• Products:
•
•
•
Example:
NaHCO
3
(aq) + HCl (aq) 
14

Acid & Active Metals
•
•
•
•
Example: calcium solid + HCl
Zn and HCl
15

Titration
• Indicator:
Colorless
(acidic)
• Equivalence Point:
• End Point:
Pink
(basic)
16

Titration Calculations
25.0 mL HCl solution is titrated with 15.5 mL 0.200 M
NaOH to reach the equivalence point.
What is the molarity of the HCl?
mols base?
mols acid?
Acid concentration?
17

Buffers
•
• Acid must neutralize __________________________
• Base must neutralize __________________________
• Acid and base must not __________________________
18

Buffers
CH
3
COOH (aq) + H
2
O (l) CH
3
COO
-
(aq) + H
3
O + (aq)
You have prepared a buffer with 0.90 M CH
3
1.2 M CH
3
COO-. (K a
COOH and for acetic acid = 1.8 x 10 -5 ).
What is the equilibrium expression for this buffer?
What is the [H
3
O + ] in this solution?
What is the pH of this solution?
19