1. CHAPTER 14
AP CHEMISTRY

2. NATURE OF ACIDS AND BASES
Acids - sour
Bases (alkali) - bitter and slippery
Brønsted-Lowry
Acid is a proton [H+] donor, base is a proton acceptor
H+ never found in water, will always form the hydronium ion
HA(aq) + H2O(l) --> H3O+(aq) A-(aq)
Acid Base Conj. Acid Conj. Base
ka = [H+][A-]
[HA]
Diprotic acid - forms two protons
Page 641 table 14.1

3. Continue Carboxyl group Page 642 table 14.2
Arrange the following species to strength as a base H2O, F-, CN-, Cl-, NO2-
Weakest Cl- < H2O < F- < NO2- < CN- strongest Strong Weak carbon
Acid specator Acid Containing

4. WATER AS AN ACID OR BASE Amphoteric - can be either an acid or base
OH- — H2O — H3O+
NH2- — NH3 — NH4+
Any aqueous solution that contains H3O+ ions and OH- ions will eventually reach equilibrium
2 H2O <==> H3O+(aq) + OH-(aq)
kw = [ H3O+][OH-]
[H2O ]

5. Continue
Any pure solids or liquids do not have concentrations, therefore they are not placed in the equation
kw = [ H3O+][OH-] = 1.0 X at 25 °C
When [ H3O+] = [OH-] = 1.0 X 10-7 a reaction will be neutral
[ H3O+] < [OH-] the solution is basic
[ H3O+] > [OH-] the solution is acidic
Calculate the [H3O+] or [OH-] opposite of what you have and state if the solution is neutral, acidic, or basic
2.0 X 10-5 M H3O+
3.0 X 10-9 M OH-
1.0 X 10-7 M OH-
Orange juice demo

6. pH SCALE
pH = -log [H+]
Significant figures of the concentration is equal to the number of places after the decimal point.
1.0 X 10-9 two sig. figs. so the pH will have two decimal places pH = 9.00
pOH = -log[OH-]
pk = -log k
[H+] = 10-pH
pH = 7 neutral, pH < 7 acidic, pH > 7 basic

7. PROBLEMS What if [H+] = 2.4 X 10-6M, what would the pH be?
-log (2.4 X 10-6M) = 5.62 = pH
What if [OH-] = 1.4 X 10-5M. Calculate the pH
pH = 9.15
What will the H+ concentration be if a solution has a pH of 8.68?
[H+] = 10-pH = 2.1 X 10-9 M
Page 646 figure 14.3

8. STRONG ACIDS HCl, HNO3, H2SO4, HClO4, HClO3
Look for the major components found in the solution
HCl(aq) has H+, Cl-, and H2O
Look at what can give H+
H2O <=> H+ + OH-
HCl ---> H+ + Cl-
Water gives such a small amount of hydrogen ions we can ignore it

9. WEAK ACID
HF(aq) species are H+, F-, H2O. Look at those which can give H+
HF(aq) <=> H+ (aq) + F-(aq) ka = 7.2 X 10-4
H2O(aq) <=> H+(aq) + OH-(aq) ka = 1 X 10-14
HF is a weak acid but it is stronger than water so it is the dominant source of H+
HX(aq) + H2O(aq) <=> H3O+(aq) + X-(aq)
ka = [ H3O+][X-]
[HX]

10. PROBLEM
A student prepared a 0.10 M solution of formic acid, HCHO2, and measured its pH using a pH meter. The pH at 25 °C was 2.38
Calculate ka
What percent of acid was dissociated?
[H+] = 10-pH = 4.2 x 10-3
HCHO2 <=> H CHO2-
Initial M
Change x x x 10-3
Equilibrium x x x 10-3
ka = (4.2 x 10-3)2 = 1.8 X 10-4
( x 10-3) <-- The 4.2 x 10-3 is so small ignore it
[H+] X 100 = 4.2 x 10-3 = 4.2%
[HCHO2]

11. Continue Calculate [H+] in solution
Find [H+] in M HC2H3O2. ka = 1.8 X 10-5
HC2H3O2 <=> H+ + C2H3O2-
[H+] = [C2H3O2-] = X
[HC2H3O2] = X assume that this X is small
X2/0.200 = 1.8 X 10-5
X = 1.9 X 10-3
Check (1.9 X 10-3)/0.200 X 100 = if this number is less than 5% then OK. If not make another approximation
Find [H+] in 0.100M HF (6.9 X 10-4)
8.3 X 10-3
You get a larger % error than 5%, so do again
X2/( ) = 6.9 X 10-4
8.0 X 10-3

12. Continue Go over example page 654
% dissociation = amount dissociated X 100
Initial concentration
Page 658 example
STRONG BASES - group 1 metals, calcium, barium, and strontium
SO2 + H2O <=> H2SO3
nonmetal oxide acid
Ca(OH)2(aq) + H2SO3(aq) <=>CaSO3(s) + H2O(l)
strong base weak acid Salt Water
CaO(s) + H2O(l) <=> Ca(OH)2(aq)
metal oxide Base

13. AMINE GROUPS B(aq) + H2O(l) <=> BH+(aq) + OH-(aq) ka= [BH+][OH-]
Page 662 table 14.3
Page 663 example
ka X kb = kw

14. POLYPROPTIC ACID Can furnish more than one proton
H3PO4 <=> H+ + H2PO4- ka = 7.5 X 10-3
H2PO4- <=>H+ + HPO42- ka = 6.2 X 10-8
HPO42- <=> H+ + PO ka = 4.8 X 10-13
With each proton lost the ka becomes smaller
Page 666 table 14.4
Page 666 example
Oxides are strong bases
O2- + H2O <=> 2OH-

15. ACID-BASE PROPERTIES OF SALT SOLUTIONS
Cations
Spectators - derived from a strong base
Li+, Na+, K+, Ca2+, Sr2+, Ba2+
Acidic - all other cations (transition metals included)
Anions
Spectators - derived from a strong acid
Cl-, Br-, I-, NO3-, ClO4-, SO42-
Basic - derived from a weak acid
F-, NO2-, CO32-
What will the pH be for salts?
Salt Cation Anion pH
NaNO Na NO Neutral
KF K F Basic
FeCl Fe Cl Acidic
If the cation is acidic and anion basic, you look at their ka and kb

16. ACID-BASE CHARACTERS
Any molecule with a H-X bond can be an acid IF TWO rules are followed
1) polar bond and 2) strength of bond
In general metal hydrides are basic or have no acid-base properties
Nonmetal hydrides are acidic or have no acid- base properties
Pages 673 and 675 examples and tables 14.5, 14.6, 14.7