1. Types of Chemical Reactions
Predicting Chemical Reactions

2. Types of Reactions
Many chemical reactions have defining characteristics which allow them to be classified as to type.

3. Types of Chemical Reactions
The five types of chemical reactions in this unit are:
 Synthesis (S)
 Decomposition (D)
 Single Displacement (SD)
 Double Displacement (DD)
 Combustion (C)

4. Synthesis Reactions 2Mg + O2  2MgO
Two or more substances combine to form one substance.
The general form is A + X AX
Example:
Magnesium + oxygen  magnesium oxide
2Mg + O2  2MgO

5. Synthesis Reactions
Synthesis reactions may also be called composition or combination reactions.
Combination of elements
K + Cl2  KCl
ONLY One product will be formed

6. Decomposition Reactions
One substance reacts to form two or more substances.
The breaking apart of a compound into smaller elements or smaller compounds.
The general form is AX  A + X

7. Decomposition Reactions
There are 5 general Types of Decomposition Reactions:
Decomposition of a binary compound
When the right energy is applied to a binary compound it will break apart into its respective elements.
2NaCl  2Na + Cl2
Water can be decomposed by electrolysis.
2H2O  2H2 + O2

8. Decomposition Reactions
Types of Decomposition Reactions:
Decomposition of carbonates
When heated, carbonates break down to form the metal oxide and carbon dioxide.
CaCO3  CaO + CO2
H2CO3  H2O + CO2

9. Decomposition Reactions
Types of decomposition reactions:
Decomposition of metallic hydroxide
Some metal hydroxides decompose into metal oxides and water when heated.
Ca(OH)2  CaO + H2O
Note that this is the reverse of a similar synthesis reaction.

10. Decomposition Reactions
Types of decomposition reactions:
Decomposition of metallic Chlorates
Metal chlorates decompose into the metal chlorides and oxygen when heated.
2KClO3  2KCl + 3O2
Zn(ClO3)2  ZnCl2 + 3O2
Some of these reactions are used in explosives.

11. Decomposition Reactions
Types of decomposition reactions:
Decomposition of Oxy-Acids and Bases
Oxy-acids decompose into
water and the non-metal oxide.
H2SO3  H2O + SO2
Ammonium hydroxide is actually ammonia gas dissolved in water.
NH4OH  NH3 + H2O

12. Single Displacement Reactions
A metal will replace a metal ion in a compound.
The general form is A + BX  AX + B
A nonmetal will replace a nonmetal ion in a compound
The general form is Y + BX  BY + X
Cations replace Cations
Anions replace Anions

13. Single Displacement Reactions
Examples:
Ni + AgNO3 
Nickel replaces the metallic ion Ag+.
The silver becomes free silver and the nickel becomes the nickel(II) ion.
Ni + AgNO3  Ag + Ni(NO3)2
Balance the equation:
Ni + 2AgNO3  2Ag + Ni(NO3)2

14. Double Displacement Reactions
Ions of two compounds exchange places with each other.
The general form is
AX + BY  AY + BX
Cations replace Cations
Anions replace Anions

15. Double Displacement NaOH + CuSO4  The Na+ and Cu2+ switch places.
Na+ combines with SO42- to form Na2SO4.
Cu2+ combines with OH- to form Cu(OH)2
NaOH + CuSO4  Na2SO4 + Cu(OH)2
Balanced
2NaOH + CuSO4  Na2SO4 + Cu(OH)2

16. Methane, CH4, is natural gas.
Combustion Reaction
When hydrocarbon compounds are burned in oxygen, the products are water and carbon dioxide.
Methane, CH4, is natural gas.
CH4 + O2  CO2 + H2O
balanced
CH4 + 2O2  CO2 + 2H2O

17. Combustion Reactions
Combustion reactions involve light and heat energy released.
Natural gas, propane, gasoline, etc. are burned to produce heat energy.
Most of these hydrocarbon reactions produce water and carbon dioxide.

18. Show the combustion of Propane (C3H8)
Combustion Reactions
Show the combustion of Propane (C3H8)
C3H8 + O2  H2O + CO2
C3H O2  4H2O + 3CO2

19. Practice Classify each of the following as to type: 1) H2 + Cl2  2HCl
 Synthesis
2) Ca + 2H2O  Ca(OH)2 + H2
 Single displacement

20. Practice 3) 2CO + O2  2CO2 4) 2KClO3  2KCl + 3O2
 Synthesis and combustion
4) 2KClO3  2KCl + 3O2
 Decomposition

21. Practice Zn + 2HCl  ZnCl2 + H2 5) FeS + 2HCl  FeCl2 + H2S
 Double displacement
6) Zn + HCl  ?
 Single displacement
Products?
Zn + 2HCl  ZnCl2 + H2

22. Single Displacement Reactions
Not all single displacement reactions that can be written actually happen.
The metal or non-metal must be more active than the ion it is replacing.
It will depend upon the element’s Activity as determined by the Activity Series (Sec. 3)

23. Single Displacement/ Replacement Reactions
An active nonmetal can replace a less active nonmetal.
The halogen (F2, Cl2, Br2, I2) reactions are good examples.
F2 is the most active and I2 is the least.
Cl2 +2 NaI  2 NaCl + I2