1. Chapter 4: Types of Chemical Reactions
Goals:
To be able to predict chemical reactivity.
To know how to synthesize specific compounds.

2. Types of Reactions Acid-Base: proton-transfer
Oxidation-Reduction: electron-transfer
Precipitation: formation of insoluble salts
Gas Forming
Organic:
Substitution
Addition
Elimination

3. Reactions in Aqueous Solution
Unless mentioned, all reactions studied this and next week occur in aqueous solution.

4. Electrolytes
Strong Electrolytes: solute breaks apart to give ions in solution.
NaCl  Na+ + Cl-
Weak Electrolytes: solute partially breaks apart to give ions.
CH3CO2H  CH3CO2- + H happens less than 5%
Nonelectrolytes: no ions formed.
CH3CH2OH

5. Brønsted-Lowery Acid-Base Definitions
An acid is a substance that donates a proton (H+) to a base
A base is a substance that accepts a proton (H+) from an acid

6. Brønsted-Lowery Definitions
acid: donates a proton (H+) to a base
base: accepts a proton (H+) from an acid
Acid-base reactions can be reversible: reactants  products or products  reactants

7. Brønsted-Lowery Definitions
An acid is a substance that donates a proton (H+) to a base
A base is a substance that accepts a proton (H+) from an acid
Acid-base reactions can be reversible: reactants  products or products  reactants

8. Important Acids and Bases
Strong Acids:
HCl hydrochloric
HBr hydrobromic
HI hydroiodic
HNO3 nitric
H2SO4 sulfuric
HClO4 perchloric
Weak Acid:
CH3CO2H acetic
Any other acids are WEAK
Strong Bases:
LiOH lithium hydroxide
NaOH sodium hydroxide
KOH potassium hydroxide
Ca(OH)2 calcium hydroxide
Ba(OH)2 barium hydroxide
Weak Base:
NH3 ammonia

9. STRONG acids in water: 100% of acid molecules form ions:
HCl(aq) + H2O(l)  H3O+(aq) + Cl-(aq)
H3O+ is
hydronium ion

10. WEAK acids in water, ~5% or less of acid molecules form ions (acetic, H3PO4, H2CO3)

11. Polyprotic Acids multiple acidic H atoms
H2SO4  H+ + HSO4-
HSO4-  H+ + SO42-
Not all H’s are acidic:
CH3CO2H

12. Bases Strong bases are hydroxide salts
For now, the only important weak base is NH3.

13. If H3PO4 reacts as an acid, which of the following can it not make?

14. If C2O42- reacts in an acid-base reaction, which of the following can it not make?
1. H2C2O4
2. HC2O4-
3. 2 CO2

15. Acid-Base Reactions Strong Acid + Strong Base
HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l) acid base “salt” water

16. Acid-Base Reactions Diprotic Acids or Bases H2SO4(aq) + NaOH(aq) 
H2SO4(aq) Ba(OH)2(aq) 
HCl(aq) + Ba(OH)2(aq) 

17. Acid-Base Reactions Strong Acid + Weak Base
HCl(aq) + NH3(aq)  NH4Cl(aq)

18. Acid-Base Reactions Weak Acid + Strong Base
HCN(aq) + NaOH(aq)  NaCN(aq) + H2O(l) acid base “salt” water

20. Net Ionic Equations HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l)
What really happens:
H+(aq) + OH-(aq)  H2O(l)
Sodium ion and chloride ion are “spectator ions”

21. Reactions involving weak bases
HCl(aq) + NH3(aq)  NH4+(aq) + Cl-(aq)
Net-Ionic Equation:
NH3(aq) + H+(aq)  NH4+(aq)

23. CH3CO2H(aq) + NaOH(aq)  1. CH3CO2H2+(aq) + NaO(aq)
2. CH3CO2-(aq) + H2O(l) + Na+(aq)
3. CH4(g) + CO2(g) + H2O(l)

24. HCN(aq) + NH3(aq)  1. NH4+(aq) + CN-(aq) 2. H2CN+(aq) + NH2-(aq)
3. C2N2(s) + 3 H2(g)

26. Solution Concentration: Molarity
Molarity = moles solute per liter of solution
0.30 mol NH3 dissolved in L Concentration =
Written like: [NH3] = 0.60 M

27. pH Scale
In pure water, a few molecules ionize to form H3O+ and OH– H2O + H2O  OH– + H3O+
In acidic and basic solutions, these concentrations are not equal acidic: [H3O+] > [OH–] basic: [OH–] > [H3O+] neutral: [H3O+] = [OH–]

28. pH Scale Measure how much H3O+ is in a solution using pH
pH < 7.0 = acidic
pH > 7.0 = basic
pH = 7.0 = neutral
Measure of H3O+ and OH– concentration (moles per liter) in a solution
As acidity increases, pH decreases

29. pH Scale
The pH scale is logarithmic: log(102) = log(101) = log(100) = –1 log(10–1) = – –2 log(10–2) = –2
pH = –log [H3O+]
pH if [H3O+] = 10–5? 10–9? Acidic or basic?
pH if [H3O+] = M?

31. Finding [H3O+] from pH
[H3O+] = 10-pH
What is [H3O+] if pH = 8.9?

32. pH: Quantitative Measure of Acidity
Acidity is related to concentration of H+ (or H3O+)
pH = -log[H3O+]