Classification of Chemical Reactions
I. Synthesis or Direct Combination:
 Definition: Two (2) or more substances
combine to form ONE PRODUCT.
 Rxn Types:
1. Element + Element → Compound
 metal + nonmetal → binary ionic
 nonmetal + nonmetal → binary molecular
2. Element + Compound → Compound
3. Compound + Compound → Compound
II. Decomposition:
 Definition: One reactant breaks apart into
two or more substances (products).
Usually requires some form of energy.
(heat, light, electricity, etc.)
 Rxn Types:
1. Compound → Element + Element
 binary ionic → metal + nonmetal
 binary molecular → nonmetal + nonmetal
2. Compound → Compound + Element
3. Compound → Compound + Compound
III. Single Replacement(Displacement):
 Definition: One element replaces another
(similar element) from a compound.
NOTE: Active metal(nonmetal) replaces less
active metal(nonmetal) or hydrogen from a
compound in aqueous solution.*
 Rxn Types:
Compound + Element → Element + Compound
 AB
+ C →
(A & C = metals)
CB +
A
 AB
+ C → AC +
(B & C = nonmetals)
B
*Activity Series will be used for determining this.
IV. Double Replacement(Displacement) or
Metathesis:
Definition: Two ionic compounds in
aqueous solution have the (+) and (–) ions
“switch” partners to form two (2) new
compounds.
 Rxn Types:
Compound + Compound → Compound + Compound
 AX
+ BY →
(A & B = + ions)
AY +
BX
These reactions result in the formation of one of the following
products:
1. Precipitate
2. Water
3. insoluble gas
V. Combustion:
Definition: A hydrocarbon and oxygen gas
(O2) react to produce water and carbon
dioxide or carbon monoxide.
 Rxn Types:
Complete:
Hydrocarbon + oxygen → water + carbon dioxide
Incomplete:
Hydrocarbon + oxygen → water + carbon monoxide
VI. Oxidation-Reduction (Redox): For right now, anything that
doesn’t fit the above 5 categories.
To Identify a reaction as Oxidation-Reduction:
 Assign oxidation numbers to all elements in the reaction.
 Use oxidation numbers to determine:
1. Element being OXIDIZED- This will be the element
that loses electrons and its oxidation number
becomes more positive(+).
2. Element being REDUCED- This will be the element
that gains electrons and its oxidation number
becomes more negative(–).
3. OXIDIZING AGENT- This will be the chemical
substance that contains the element being reduced. It
causes another substance/element to be oxidized.
4. REDUCING AGENT- This will be the chemical
substance that contains the element being oxidized.
It causes another substance/element to be reduced.