1. Acid-Base Equilibrium
Chapter 18

2. Acids and Bases Arrhenius acids: generate H+ in water
bases: generate OH- in water
Brønsted-Lowry
acids: H+ donors
bases: H+ acceptors
HCl H2O  Cl H3O+
acid base

3. H3O+ = H+(aq) = proton in water

6. Conjugate acid-base pairs
Conjugate base:
remains after H+ is lost
acid: HCl conj. base: Cl-
Conjugate acid:
remains after H+ is gained
base: NH3 conj. acid: NH4+
Conjugate Pair
Acid
Base +
Base
Acid +
Conjugate Pair

9. Strong and Weak Acids
Strong: 100% dissociation
good H+ donor
equilibrium lies far to right (HNO3)
generates weak base (NO3-)
Weak: <100% dissociation
not-as-good H+ donor
equilibrium lies far to left (CH3COOH)
generates strong base (CH3COO-)

11. Relative Acid Strength Relative Conj. Base Strength
Very strong
Very weak
Strong
Weak
Weak
Strong
Very weak
Very strong

12. Acid Dissociation Constant

14. Strength vs. Ka
Ka Increases

15. Water is amphoteric
Acid Base Conj. Acid Conj. Base

16. Proton Transfer in WaterH + -

17. [H3O+] and [OH-] [H3O+] 1x100 to 1x10-14 in water
[OH-] 1x10-14 to 1x100 in water

18. Finding [H3O+] and [OH-]

19. pH Scale
pH to in water
pOH to in water
pKw = pH + pOH =

20. H+ OH- pH and pOH As [H3O+] rises, [OH-] falls As pH falls, pOH rises
Acidic Neutral Basic
As pH falls, pOH rises

24. Indicators

26. Polyprotic Acids 1. H3PO4 H2PO4- + H+ Ka1 = 7.2 x 10-3
3. HPO PO H+
Ka3 = x 10-13
Ka1 > Ka2 > Ka3

28. Strength of Bases Strong: 100% dissociation OH- supplied to solution
NaOH(s)  Na+(aq) + OH-(aq)
Weak:
<100% dissociation
OH- by reaction with water
CH3NH2(aq) + H2O(l) CH3NH2(aq) + OH-(aq)

31. Base Dissociation Constant

32. Kw, Ka and Kb

35. Structure and Acid-Base Behavior
Binary hydrides:
1. Bond polarity (high  acid strength)
2. Bond strength (low  acid strength)

37. Structure and Acid-Base Behavior
Binary oxides:
1. Acidic oxides (acid anhydrides)
O—X bond: strong and polar
SO2, SO3, NO2, P4O10, …
2. Basic oxides (basic anhydrides)
O—X bond: ionic
K2O, CaO, …

38. Structure and Acid-Base Behavior
Oxoacids (HaXbOc):
1. Same number of O on different X
EN of X
2. Different number of O on same X
more O

39. Relative Strengths of Oxoacids

40. Increasing Acid StrengthCl O H
1 O
Electron density O Cl O H
2 O
Electron density O Cl O H O
3 O
Electron density O O Cl O H
4 O O
Electron density
Increasing Acid Strength

41. Lewis Acids and Bases Lewis Acid: electron pair acceptor
Lewis Base: electron pair donor A l 3 + 6 H O
Acid Base