1. I. Types of Chemical Reactions ()
Ch. 9 – Chemical Reactions
I. Types of Chemical Reactions ()

2. Symbols used in equations
the arrow separates the reactants from the products 
Read “reacts to form”
The plus sign = “and”
(s) after the formula -solid
(g) after the formula -gas
(l) after the formula –liquid
(aq) dissolved in water

3. CH4(g) + 2O2(g)  CO2(g) + 2H2O(g)
A. Combustion
the burning of any substance in O2 to produce heat
A + O2  B
CH4(g) + 2O2(g)  CO2(g) + 2H2O(g)

4. Reactants Must Come In Contact with Each Other
Molecules and atoms of the reactants must come into contact with each other for a reaction to take place.
Example: When a safety match is lighted.
One reactant, potassium chlorate (KClO3) is on the match head.
The other reactant, phosphorus, P4, is on the striking surface of the matchbox.
The reaction begins when the two substances come together by rubbing the match head across the striking surface.
If the reactants are kept apart, the reaction will not happen.

5. A. Combustion 4Na(s)+ O2(g)  2Na2O(s) C3H8(g)+ O2(g)  5 3 4
Products:
contain oxygen
hydrocarbons form CO2 + H2O
4Na(s)+ O2(g) 
2Na2O(s)
C3H8(g)+ O2(g) 
CO2(g)+ H2O(g)

6. B. Synthesis
the combination of 2 or more substances to form a compound
only one product
A + B  AB

7. B. Synthesis
H2(g) + Cl2(g)  2 HCl(g)

8. Al(s)+ Cl2(g)  2 3 2 AlCl3(s) B. Synthesis Products:
ionic - cancel charges
covalent - hard to tell
Al(s)+ Cl2(g) 
AlCl3(s)

9. AB  A + B C. Decomposition
a compound breaks down into 2 or more simpler substances
only one reactant
AB  A + B

10. C. Decomposition
2 H2O(l)  2 H2(g) + O2(g)

11. C. Decomposition 2 2 KBr(l)  K(s) + Br2(l) Products:
binary - break into elements
others - hard to tell
KBr(l) 
K(s) + Br2(l)

12. A + BC  B + AC D. Single Replacement
one element replaces another in a compound
metal replaces metal (+)
nonmetal replaces nonmetal (-)
A + BC  B + AC

13. Cu(s) + 2AgNO3(aq)  Cu(NO3)2(aq) + 2Ag(s)
D. Single Replacement
Cu(s) + 2AgNO3(aq)  Cu(NO3)2(aq) + 2Ag(s)

14. D. Single Replacement Fe(s)+ CuSO4(aq)  Cu(s)+ FeSO4(aq)
Products:
metal  metal (+)
nonmetal  nonmetal (-)
free element must be more active (check activity series)
Fe(s)+ CuSO4(aq) 
Cu(s)+ FeSO4(aq)
Br2(l)+ NaCl(aq) 
N.R.

15. AB + CD  AD + CB E. Double Replacement
ions in two compounds “change partners”
cation of one compound combines with anion of the other
AB + CD  AD + CB

16. Pb(NO3)2(aq) + K2CrO4(aq)  PbCrO4(s) + 2KNO3(aq)
E. Double Replacement
Pb(NO3)2(aq) + K2CrO4(aq)  PbCrO4(s) + 2KNO3(aq)

17. E. Double Replacement Pb(NO3)2(aq)+ KI(aq)  2 2 PbI2(s)+ KNO3(aq)
Products:
switch negative ions
one product must be insoluble (check solubility table)
Pb(NO3)2(aq)+ KI(aq) 
PbI2(s)+ KNO3(aq)
NaNO3(aq)+ KI(aq) 
N.R.