6.1-6.2 Reaction Types
Synthesis, Decomposition and
Combustion
Types of Chemical Reactions
There are 6 ways elements and
compounds may interact
 You can predict the products of a
reaction if you can identify the reactants
you are using
 General chemical equations (GCE) use
letters in the place of the symbols of
elements. They help you identify the
reaction type

Symbols in GCE

A single letter is a metal or non-metal Ex. A,
B, X
 H is for the hydrogen in an acid
 OH is for hydroxide in a base
 Two letters Ex. AB, CD represent a compound
Example:
GCE: HB + XOH  XB + H2O
Word equation: sulfuric acid + sodium hydroxide  sodium sulfate + water
Skeleton equation: H2SO4 (aq) + NaOH (s)  Na2SO4 (aq) + H2O (l)
Balanced Equation: H2SO4 (aq) + 2 NaOH (s)  Na2SO4 (aq) + 2 H2O (l)
1. Synthesis Reactions
Element + Element  Compound
In general A + B AB
Example: Mg (s) + O2 (g)  MgO (s)
S8 (g) + O2(g)  SO2 (g)
H2 (g) + N2 (g)  2NH3 (g)
2. Decomposition Reactions
A compound is broken down into two or
more elements or simpler compounds
Compound  Element + Element
In general, AB A + B

Example: 2 HgO (s)  2 Hg (l) + O2(g)
2 H2O (l)  2 H2 (g) + O2 (g)
3.Combustion Reactions
A compound or element rapidly reacts
with oxygen gas
 Heat and light are given off
 Usually involve a hydrocarbon (a
compound made up of only hydrogen
and carbon)
 The formula for a hydrocarbon is general
CxHy (x and y are subscript numbers)
Ex. CH4 is methane

Combustion
A. Complete combustion
-plenty of oxygen is available
In general, CxHy (g)+ O2 (g) CO2 (g) + H2O (l)
Incomplete combustion
-Oxygen is in limited supply
B.
In general,
CxHy (g)+ O2 (g) C(s) + CO (g) + CO2 (g) + H2O (l)
Impact on the Environment
Global warming – the combustion of
hydrocarbons releases carbon dioxide, a
greenhouse gas
 Cleaning oil spills – on land, the oil can
be set on fire (combustion) then the
contaminated soil is removed for
additional treatment

Determine the reaction type
2 Na + Cl2  2 NaCl
Type:
CH4 + 2 O2  CO2 + 2 H2O
Type:
2NI3  N2 + 3 I2
Type:
Predict the Products
1.
2.
3.
NH3 
Na + Cl2 
S8 + O2 
Type:_______
Type:_______
Type:_______
plenty
4.
CH4 + O2 
Type:_______
deficient
5.
C 2H 6 + O2 
Type:_______
Homework
p. 229 #4-10