1. Chemistry B11
Chapter 8
Acids and Bases

2. DRANO Acids and Bases Acids: sour, squeaky clean
Bases: bitter or salty, dirty slimy
DRANO

3. Acids and Bases Acid: produces H3O+ Arrhenius definition:
CH3COOH(aq) + H2O(l) CH3COO-(aq) + H3O+(aq)
H3O+ (Hydronium ion):
H+(aq) + H2O(l) H3O+(aq)
Base: produces OH-
H2O
NaOH(s) Na+(aq) + OH-(aq)
NH3(aq) + H2O(l) NH4+(aq) + OH-(aq)
Most Acids release or donate H+ Bases accept H+

4. Acids and Bases
Bronsted and Lowry definition: (If H2O is not involved.)
Acid: donates H+ (proton)
Base: accepts H+ (proton)
CH3COOH + NH3 CH3COO- + NH4+
acid
base
Conjugate
Conjugate acid-base pair

5. Acids and Bases HCl + H2O Cl- + H3O+ C6H5OH + H2O C6H5O- + H3O+ acid
Conjugate
base
Conjugate
acid
Conjugate acid-base pair
Conjugate acid-base pair
C6H5OH + H2O C6H5O H3O+
acid
base
Conjugate
base
Conjugate
acid
Conjugate acid-base pair
Conjugate acid-base pair

6. Weak acid or base: is partially ionized in aqueous solution.
Acids and Bases
Weak acid or base: is partially ionized in aqueous solution.
produces less H+ and OH-
CH3COOH(aq) + H2O(l) CH3COO-(aq) + H3O+(aq)
NH3(aq) + H2O(l) NH4+(aq) + OH-(aq)
Strong acid or base: is completely ionized in aqueous solution.
produces more H+ and OH-
HCl(aq) + H2O(l) Cl-(aq) + H3O+(aq)
NaOH(aq) + H2O(l) Na+(aq) + OH-(aq)

7. Acids and Bases
A strong acid contains a weak conjugate base.

8. Acids and Bases Monoprotic acids HCl Diprotic acids H2SO4
Triprotic acids
H3PO4
Amphiprotic: it can act as either acid or a base.
HCl(aq) + H2O(l) Cl-(aq) + H3O+(aq)
NaOH(aq) + H2O(l) Na+(aq) + OH-(aq)
base
acid

9. Naming binary acids Hydro -ide ion -ic acid Anion : + HF
F-: flouride ion Hydroflouric acid
HCl
Cl-: chloride ion Hydrochloric acid
H2S
S2-: sulfuride ion Hydrosulfuric acid

10. Naming ternary acids -ite ion -ous acid Anion: -ate ion -ic acid HNO2
NO2-: Nitrite ion Nitrous acid
HNO3
NO3-: Nitrate ion Nitric acid
H2CO3
CO32-: carbonate ion carbonic acid
H2SO3
SO32-: sulfite ion sulfurous acid

11. Strong acid pKa < -2 / Weak acid pKa -2 to 12
Ionization constant
HA + H2O A- + H3O+
[A-] [H3O+]
Equilibrium constant
K =
not for strong acids
[HA] [H2O]
Ka = K [H2O] =
[A-] [H3O+]
[HA]
Acid ionization constant
Ka < 1
- Log Ka = pKa
Strong acid pKa < -2 / Weak acid pKa -2 to 12
Ka ↑ or pKa ↓
Stronger acid

12. pH and pOH pH = - log [H3O+] or -log [H+] pOH = - log [OH-]
pH scale:
Log 100 = 2 7 14
Acid
Neutral
Base
[H3O+] ↑
[H3O+] ↓ and [OH-] ↑

13. pH and pOH H2O + H2O OH- + H3O+ KW = [H3O+] [OH-] = (1×10-7) (1×10-7)
pH + pOH = 14

14. pH meter and pH indicators

15. Nature & pH indicators Bigleaf Hydrangea In basic soil (alkaline)
In acidic soil

16. Acid Reactions
1. Reaction with metals (strong acids): a salt and H2 are produced.
Mg(s) + 2HCl(aq) MgCl2(aq) + H2(g)
2. Reaction with metal hydroxides: a salt and water are produced.
KOH(aq) + 2HCl(aq) KCl(aq) + H2O(l)

17. Acid Reactions 3. Neutralization: reaction between an acid and a base.
A salt and water are produced.
KOH(aq) + 2HCl(aq) KCl(aq) + H2O(l)
2NaOH(aq) + H2SO4(aq) Na2SO4(aq) + 2H2O(l)
Strong acid reacts with strong base
to produce the weaker acid and weaker base.
(This is the direction of a reaction)

18. Titration (Neutralization reaction)B A
MB: known
VB: known
MA: unknown
VA: known
Equivalence point:
Equal amount of acid (H+) and base (OH-) (pH = 7).
2NaOH + 1H2SO4  2NaSO4 + 2H2O
MA × VA MB × VB =
Coefficient A
Coefficient B

19. Buffers pH stays constant. Buffer
Acid or Base
pH stays constant.
Buffer
A buffer resists changes in pH when limited
amounts of acid or base are added.

20. Buffers Our blood is a buffer solution. pH of blood ≈ 7.4
Acid
pH of blood ≈ 7.4
Acid
Base
Shock Absorber

21. Acetic acid / Sodium acetate
Buffer Composition
Weak Acid + its Conjugate base (in equilibrium)
salt of the weak acid
CH3COOH + CH3COO-Na+
CH3COOH / CH3COO-
Acetic acid / Sodium acetate
Acetic acid / Acetate ion pair

22. Buffers Carbonate buffer H2CO3 / HCO3-
Phosphate buffer H2PO4- / HPO42-
Proteins buffer

23. How do buffers work? HCO3- + H3O+ → H2CO3 + H2O
Carbonate buffer H2CO3 / HCO3-
If we eat an acidic food:
HCO3- + H3O+ → H2CO3 + H2O
H2CO3 + OH- → HCO3- + H2O
If we eat a basic food:

24. Henderson-Hasselbalch equation
pH of Buffers
HA(aq) A-(aq) H+(aq)
Weak acid
Conjugate base
[A-]
pH = pKa + log
[HA]
Henderson-Hasselbalch equation
[HA]: concentration of the weak acid
[A-]: concentration of its conjugate base
pKa of the weak acid