1. Chemical Reaction Types

2. Types of reactions Synthesis (Composition) Decomposition Combustion
Single-Replacement
Double-Replacement
Precipitation and Solubility
Acid-Base
Reduction-Oxidation (Redox)

3. Synthesis (Composition)
Two or more substances combine to form a new compound
A + X  AX
Examples:
Fe + S → FeS
H2 + SO3 → H2SO3

4. Decomposition One compound forms two or more simpler substances
AX  A + X
Examples:
Metallic carbonate → metal oxide + CO2
CaCO3 → CaO + CO2
Metallic hydroxide → metal oxide + H2O
Ca(OH)2 → CaO + H2O
Metallic chlorate → metal chloride + O2
2 KClO3 → 2 KCl O2

5. Combustion
A substance combines with oxygen releasing a large amount of energy in the form of heat and light
Does not have a true generic form, but hydrocarbons will combust in the presence of oxygen to produce CO2 and H2O
Hydrocarbon + O2 → CO­­2 + H2O

6. Single-Replacement 1 element replaces a similar element in a compound
A + BX  AX + B or Y + BX  BY + X
Examples:
Replacement of a metal with a more active metal
Zn + CuSO4 → Cu + ZnSO4
Replacement of hydrogen in water by a metal
Ca H2O → H2 + Ca(OH)2
Replacement of hydrogen in an acid by a metal
Zn + H2SO4 → H2 + ZnSO4
Replacement of less active halogen by a more active halogen
F > Cl > Br > I
Cl KBr → 2 KCl + Br

7. Double-Replacement
The ions of two compounds exchange places in an aqueous solution
AX + BY  AY + BX
Examples:
Formation of a gas
FeS HCl → FeCl2 + H2S ↑ (↑ means gas)
Formation of a precipitate (ppt.)
NaCl + AgNO3 → NaNO3 + AgCl ↓ (↓ means ppt.)
Formation of water
NaOH + HCl → NaCl + H2O

8. Precipitation Reactions
A reaction in which two soluble salts react to form an insoluble product is called a precipitation reaction
The insoluble product forms a solid and precipitates out of solution
The product is called a precipitate

9. Solubility Rules Most nitrate salts are soluble
Most salts of alkali metals and ammonium are soluble

10. Practice Identify the following as soluble - S or insoluble - I Na2SO4
Pb(NO3)2
PbSO4
NaNO3
KOH
Fe(NO3)3
Fe(OH)3
H2SO4
K2Cr2O7
Co(NO3)2
Identify the following as soluble - S or insoluble - I
KCl
AgNO3
AgCl
KNO3
K2CrO4
Ba(NO3)2
BaCrO4
soluble
soluble
insoluble
soluble
soluble
soluble
soluble
soluble
insoluble
insoluble
soluble
soluble
soluble
soluble
soluble
soluble
insoluble

11. Precipitation Reactions
Predicting Products
Write all reactants as their ions
Combine ions that were not combined before
Be sure to combine a single type of positive and a single type of negative ion
The total charge of the compound must be zero
If a product is insoluble, a precipitation reaction has occurred

12. Examples
Predict the products of, write and balance the following reactions. Identify any precipitates. All reactants are aqueous.
Potassium hydroxide reacts with barium nitrate
Silver nitrate reacts with potassium chloride

13. Practice
Predict the products of, write and balance the following reactions. All reactants are aqueous.
3. Potassium nitrate and barium chloride
4. Sodium sulfate and lead (II) nitrate
5. Potassium hydroxide and iron (III) nitrate

14. Practice
6a. What compound precipitates when aqueous solutions of Fe2(SO4)3 and LiOH are mixed? 6b. Write a balanced equation for the reaction. 6c. Write the complete ionic equation and the net ionic equation for the above reaction. 6d. Will a precipitate form when solutions of Ba(NO3)2 and KOH are mixed?

15. Common Acids and Bases (8th)
Strong Acids
HCl, HI, HBr
H2SO4 (1st H)
HNO3
Weak Acids
HC2H3O2 HF
HSO4-
NH4+
Strong Bases
KOH
NaOH
Weak Bases
NH3

16. Oxidation-Reduction Reactions
A reaction where electrons are transferred from one substance to another
Also called redox reactions
Used often in biological systems
All combustion reactions are redox

17. Oxidation States
To keep track of electrons in redox reactions, we track a numeric concept known as the element’s oxidation state
Oxidations states arbitrarily assign electrons to atoms and treat the atoms as if they had the charge imparted by the gain or loss of electrons

18. Oxidation States The oxidation state of:
An atom in its elemental state is zero
A monatomic ion is its charge
Fluorine is -1 in a compound
Oxygen is -2 in a compound (-1 in peroxides)
Hydrogen is typically +1 in a compound
The elements in a compound or polyatomic ion sum to its charge

19. Example Assign oxidation states to each atom in: CO2 SF6 NO3- CH4 Na
NaCl

20. Oxidation and Reduction
A substance is oxidized if its oxidation number becomes more positive (loss of electrons)
A substance is reduced if its oxidation number becomes more negative (gain of electrons)
OIL RIG or LEO GER
Oxidation and reduction are coupled reactions, if you have one, you must have the other

21. Examples
For the following reactions, assign oxidation states and identify oxidized substance and reduced substance
Ce+4(aq) + Sn+2(aq)  Ce+3(aq) + Sn+4(aq)
CH4(g) + O2(g)  CO2(g) + H2O(g)
2 Al(s) + 3I2(s)  2AlI3(s)
2 PbS(s) + 3 O2(g)  2 PbO(s) + 2 SO2(g)
PbO(s) + CO(g)  Pb(s) + CO2(g)

22. Redox Reactions
For the following reactions, assign oxidation states and identify oxidized substance and reduced substance
Cu + HNO3  CuNO3 + H2
H2 + O2  H2O
Na + FeCl2  NaCl + Fe
SiCl4(l) + Mg(s)  MgCl2(s) + Si(s)
Reduced – O : O e-  2 H2O
Oxidized – H : H2  H2O+ 2 e- => 2H2  2 H2O+ 4 e-
Molecular eq: : 2 H2 + O2  2 H2O

23. Identifying Types of Reactions
Characteristics of each type of reaction
Precipitation
Two (or more) aqueous ionic compounds
Dead giveaway: One (or more) solid, insoluble, ionic product(s)
Acid-Base
Acid reacting with base
Dead giveaway: formation of water
Redox
Transfer of electrons (write oxidation states)
Dead giveaway: element in natural state forming a compound