1. WEAK Acids & Bases have Ka & Kb and RICE
Unit 9 SUMMARY: Acid-Base Equilibria
Acid: proton (H+) donor
Base: proton (H+) acceptor
(forms conjugate base)
(forms conjugate acid)
6 Strong Acids: (completely ionize)
HCl, HBr, HI, HNO3 , H2SO4 , HClO4
8 Strong Bases: (completely dissociate)
the soluble hydroxides (OH–) of…
Group 1 (Li,Na,K,Rb,Cs) and Ca2+, Sr2+, Ba2+
WEAK Acids & Bases have Ka & Kb and RICE

2. Factors Affecting Acid Strength
larger X in H–X
stronger acid
(bond is longer, weaker)
stronger acid
(greater ∆EN)
more polar H–X bond
(weaker, likely to break and lose H+)

3. Water & pH H2O(l) + H2O(l)  H3O+(aq) + OH−(aq) H2O(l) 
H+(aq) + OH−(aq)
Kw = [H+] [OH−]
= 1.0  10–14 (at 25oC)
x2 = 1.0  10–14
[H+] = √(1.0  10−14) = 1.0  10−7
pH = −log [H+]
In pure water, pH = −log(1.0  10−7) = 7.00
Acids have higher [H+], so pH<7 (lower [OH–])
Bases have lower [H+], so pH>7 (higher [OH–])

4. pH pOH [H+] [OH–] Calculations
pH = –log[H+]
pOH = –log[OH–]
10–pH = [H+]
10–pOH = [OH–]
Kw = [H+]∙[OH–] = 1.0 x 10–14
pH + pOH = 14
Ka  Kb = Kw
(for conjugates)
Given any 1 of these 4, you know all 4 values. H+
OH– pH
pOH

5. GIVEN pH, Calculate Ka pH = −log [H3O+] 2.38 = −log [H3O+] (0.0042)2
[HCOOH]
[H3O+]
[HCOO−] I
0.10 M
0 M C E M
pH = −log [H3O+]
2.38 = −log [H3O+]
−2.38 = log [H3O+]
10−2.38 = [H3O+]
(0.0042)2
(0.10)
Ka =
[H3O+]eq = M

6. HCOOH(aq) + H2O(l)  H3O+(aq) + HCOO–(aq)
Percent Ionization
[H3O+]eq
[HA]in
NOT on equation sheet
% ionization =  100%
HCOOH(aq) + H2O(l)  H3O+(aq) + HCOO–(aq)
[HCOOH]
[H3O+]
[HCOO−] I
0.10 M
0 M C
−0.0042 E
= 0.10 M M
0.0042
0.10
% ionization =  100% =
4.2%
4.2% OF 0.10 M HCOOH IS ionized.

7. HC2H3O2(aq) + H2O(l)  H3O+(aq) + C2H3O2–(aq)
GIVEN Ka , Calculate pH
HC2H3O2(aq) + H2O(l)  H3O+(aq) + C2H3O2–(aq)
[H3O+] [C2H3O2−]
[HC2H3O2]
Ka =
= 1.8  10−5
[HC2H3O2]
[H3O+]
[C2H3O2−] I
0.30 M C E –x +x +x
0.30 – x x x
 0.30 M
(b/c K <<<1)
(x)2
(0.30)
1.8  10−5 =
x = 2.3  10−3 M H+
pH = −log [H+]

8. Cations: Anions: NH4+(aq) + H2O(l)  NH3(aq) + H3O+(aq) (acidic, ↓pH)
(donates H+)
NH4+(aq) + H2O(l)  NH3(aq) + H3O+(aq)
Cations:
(acidic, ↓pH)
Cu+(aq) + H2O(l)  CuOH(aq) + H+(aq)
Most metal cations will lower pH (acidic).
(Fe3+, Zn2+, …) (take OH– from H2O to lose H+)
But, metal cations of strong base CAN’T affect pH.
(Li+,Na+,K+,Ca2+,Ba2+) (can’t take OH– from H2O)
Anions:
(basic, ↑pH)
F−(aq) + H2O(l)  HF(aq) + OH−(aq)
Most anions will increase pH (basic) (F–, HCO3–, NO2–) (take H+ from H2O)
But, anions from conj. base of a strong acid CAN’T affect pH. (Cl–, HSO4–, NO3–) (can’t take H+ from H2O)