1. ACID - BASE CHEMISTRY What is an acid? What is a base?
hydrogen ion donor
What is an acid?
What is a base?
How does HNO3, a strong acid, behave in water?
How does HNO2, a weak acid, behave in water?
hydrogen ion acceptor
Strong electrolyte: HNO3 ---> H+ + NO %
Weak electrolyte: HNO2 = H+ + NO2- partial

2. How does NH3 behave in water?
Write a reaction for the general behavior of any weak acid.
Write a reaction for the general behavior of any weak base.
Weak electrolyte: NH3 + H2O = NH4+ + OH-
HA + H2O = H3O+ + A- or HA = H+ + A-
B + H2O = BH+ + OH-

3. How about an equilibrium constant for weak acids?
HA + H2O = H3O+ + A- or HA = H+ + A-
(H3O+) (A-)
(HA) (H2O)
(H+) (A-)
(HA)
K =
Ka =
acid dissociation constant
For dilute solutions (<1M):
(H2O) = 56 M
and is a constant

4. How about an equilibrium constant
for weak bases?
B + H2O = BH+ + OH-
(BH+) (OH-)
(B)
Kb =
base dissociation constant

5. The Bronsted-Lowry Concept
Conjugate pairs
HCl Cl-
CH3COOH CH3COO-
NH NH3
HNO3 NO3-
How does a conjugate pair differ?

6. Behavior of water at 25oC: H2O = H+ + OH- Kw = (H+)(OH-) = 1.0 x 10-14
This reaction is endothermic. Why?
What happens to Kw if temperature
increases?

7. pH pH = -log (H+) (H+) = 10-pH What is pH of 0.0271M HCl?
If pH = 3.48, what is (H+)?

8. What is the pH of pure water at 25oC?
H2O = H OH-
Kw = 1.0 x 10-14
Neutrality

9. Other useful relationships
pX = -log (X) (X) = 10-pX
_______ = -log (OH-)
______ = 10-pKa
pKw = _______
Kw = (H+)(OH-) convert to log form

10. How are pH, pOH, (H+), and (OH-) related at 25oC?
acidic
(H+) > (OH-)
neutral
(H+) = (OH-)
basic
(H+) < (OH-)

11. pH acid rain (NOx, SOx) pH of 4.2 - 4.4 in Washington DC area
0-14 scale for the chemists 2 3 4 5 6 7 8 9 10 11 12
acidic
(H+) > (OH-)
25oC
(H+) = (OH-)
distilled water
basic or alkaline
(H+) < (OH-)
normal rain (CO2)
pH = 5.3 – 5.7
fish populations
drop off pH < 6 and to zero pH < 5
natural waters pH =

12. Can you have a negative pH?
What is the pH of 6.0M HCl?
What is the pH of 10M NaOH?
What is the pH of 10-8 M HCl?

13. How about the pH of a weak acid solution?
To the CHM 102 webpage….
Good pH tutorial:

14. practice… 1. Calculate pH of 0.0016 M NaOH.
2. What is (H+) of solution with pOH =

15. 3. What is the pH of neutrality at 60oC where Kw = 9.62 x 10-14?
4. What is the pOH of neutrality at 60oC?
5. How many times more concentrated is a pH of 4 compare to a pH of 7?

16. answers… 5. 1000 x 4. pOH = 6.50 3. pH = 6.50 2. (H+) = 4.1 x 10-12 M