Types of Chemical
Reactions
SCH3U
Success Criteria
O By the end of this class you should:
O Be able to classify a reaction as synthesis,
decomposition, single displacement, double
displacement, combustion or neutralization.
O Be able to predict the products of synthesis
and decomposition reactions.
Synthesis (Combination)
Reaction
O Two or more reactants combine to form one
product
A + B  AB
Examples of synthesis
O Metal + oxygen → metal oxide
O 2Mg(s) + O2(g) →
2MgO(s)
O Nonmetal + oxygen →
O C(s) + O2(g) →
nonmetallic oxide
CO2(g)
O Metal oxide + water →
O MgO(s) + H2O(l) →
metallic hydroxide
Mg(OH)2(aq)
O Nonmetallic oxide + water →
O CO2(g) + H2O(l) →
O Metal + nonmetal →
O Mg(s) + Cl2(g) →
acid
H2CO3(aq) (one more oxygen)
ionic compound (salt )
MgCl2(s)
O A few nonmetals combine with each other.
O 2P(s) + 3Cl2(g) →
2PCl3(g)
Oxides
• When an element combines with oxygen an oxide
is formed
• Metals react with oxygen to form metal oxides
• Metal oxides
• are always solids
• react in water to form basic solutions
• are also called basic oxides
Metal Oxides - Example
2 Ca(s)
+ O2(g)
 2 CaO(s)
metal oxide
CaO(s) + H2O (l)  Ca(OH)2(aq)
basic solution
metal hydroxide
Oxides
• Non-metals react with oxygen to form
non-metal oxides
• Non-metal oxides
• are often gases or liquids
• react in water to form acidic solutions
• are also called acidic oxides
Non-metal Oxides - Example
N2 (g)
+ 2 O2(g)
 2 NO2 (g)
non-metal oxide
3 NO2 (g) + H2O (l)  2 HNO3(aq) + NO (g)
acidic solution
Summary of Predicting
Synthesis Reactions
1. Metal oxides react with water to form metal
hydroxides (bases)
2. Non-metal oxides react with water to form
oxyacids (you just add 1 more oxygen to
the oxide to form it’s oxyanion)
3. A metal and non-metal combine to form an
ionic compound (a salt)
4. Some non-metals will combine to form
covalent compounds.
Decomposition Reaction
O A single reactant is decomposed/broken
down into two or more products.
AB  A + B
Examples
O
O
Metallic carbonates, when heated, form metallic oxides & CO2(g).
MgCO3(s) →
MgO(s) + CO2(g)
O
Most metallic hydroxides, when heated, decompose into metallic
oxides and water. Ca(OH)2(s) → CaO(s) + H2O(g)
O
Metallic chlorates, when heated, decompose into metallic chlorides
and oxygen. 2KClO3(s) → 2KCl(s) + 3O2(g)
O
Some acids, when heated, decompose into nonmetallic oxides and
water.
O
O
H2SO4(aq) →
H2O(l) + SO3(g)
Some oxides, when heated, decompose.
O
O
2HgO(s) →
2Hg(l) + O2(g)
Some decomposition reactions are produced by
electricity(electrolysis).
O
O
2H2O(l) → 2H2(g) + O2(g)
2NaCl(l) → 2Na(s) + Cl2(g)
Summary of Decomposition
Reactions
1.
2.
3.
4.
5.
All binary compounds break down into their
elements
Metal carbonates decompose when heated to
form metal oxides and carbon dioxide
Chlorates decompose when heated to form
chloride compounds and oxygen gas
Bases (metal hydroxides) decompose when
heated to a metal oxide and water
Oxyacids decompose when heated to a nonmetal oxide and water