Types Of Chemical
Reactions
Objective

Distinguish between the 5 different types
of reactions

Predict the products of a reaction

Predict the physical states of products
5 Types of Reactions

Composition

Decomposition

Single Replacement

Double Replacement

Combustion
Composition Reactions

When two or more substances react to form a
single product

2 reactants → 1 product
A
+ X → AX
 2H2
+ O2 → 2H2O
 MgO
+ CO2 → MgCO3
Decomposition

Occurs when a compound is broken down into
simpler substances

Single reactant yields two or more products

(1 reactant → 2 products)

forms a common gas as a product; CO2, O2,
SO2, H2O
Decomposition Examples
 AX
→ A+ X
 2HgO
→ 2Hg + O
2
 CaCO3
→ CaO + CO2
Single Replacement

One substance replaces another

A metal replaces a metal, if it is more active

A non-metal replaces a non-metal, if it is more
active
Single Replacement Examples

A and B are metals;
A + BX → AX + B
X and Y are non-metals
OR
Y + BX → BY + X
 Mg
+ Zn(NO3)2 → Mg (NO3)2 + Zn
 Cl2
+ 2 KBr → 2 KCl + Br2
Double Replacement

An exchange of partners

The metal replaces the metal or the non-metal
replaces the non-metal
 AX
+ BY → AY + BX
 Na2S
+ Cd(NO3)2 → 2NaNO3 + CdS
 BaCl2
+ K2CO3 → BaCO3 + 2KCl
Combustion

An element or compound reacts with oxygen

Usually produces heat → Exothermic

Combustion of a hydrocarbon always produces
carbon dioxide and water
2
Mg + O2 →
2
CH3OH + 3 O2 → 2 CO2 + 4 H20 + heat
2 MgO + heat
Composition

Two elements or compounds combine to form a
single substance

A + X → AX

Fe + S → FeS

H2O + SO3 → H2SO4
5 Kinds of Decomposition
Reactions

Metallic Carbonates

Metallic Hydroxides

Metallic Chlorates

Oxy Acids

Oxides
Metallic Carbonates
CaCO3
Metal
→ CaO + CO2
oxide and carbon dioxide formed
Metallic Hydroxides

Many metallic hydroxides (OH-), when heated,
decompose into metallic oxides and water.

Ca(OH)2 → CaO + H 0
2

Metal oxide and water formed

Exceptions to the rule: NaOH and KOH
Metallic Chlorates

(ClO3-), when heated, decompose into
metallic chlorides and oxygen

2KClO3 → 2KCl + 3O2

metal chloride and oxygen formed
Oxy Acids

Some oxy acids, when heated, decompose
into nonmetallic oxides and water

Seltzer Water


H2CO3 → CO2 + H2O
Acid Rain

H2SO3 → SO2 + H2O
Oxides

Some oxides, when heated, decompose.

2HgO → 2Hg + O2

2Pb O2 → 2PbO + O2
4 Kinds of Single Replacement
Reactions

Metal w/ more active metal

Hydrogen in acids w/ more active metal

Hydrogen in water w/ by most active metals

Halogen w/ more active halogen
Metal w/ more active Metal

Replacement of a metal in a compound by a
more active metal (PCS Mazintl)

Zn + CuSO4 → ZnSO4 + Cu (s)

Zinc replaces the copper, therefore zinc is
more active
P.C.S. Mazintl
P potassium
C calcium
S sodium
M magnesium
a aluminum
z zinc
i iron
n nickel
t tin
l lead
HYDROGEN
Copper
Mercury
Silver
Activity of Halogens
Fluorine
Chlorine
Bromine
Iodine
More Active
Hydrogen in acids w/ more active
metals

Replacement of hydrogen, in acids, by metals
more active than hydrogen (PCS Mazintl)

Zn + H2SO4 → Zn SO4 + H2 (g)

The corresponding metallic compound and
hydrogen gas are formed
P.C.S. Mazintl
P potassium
C calcium
S sodium
M magnesium
a aluminum
z zinc
i iron
n nickel
t tin
l lead
HYDROGEN
Copper
Mercury
Silver
Activity of Halogens
Fluorine
Chlorine
Bromine
Iodine
More Active
Hydrogen in water w/ most active
metals

Replacement of hydrogen, in water, by the
most active metals. Which Metals?

All Group I and some of Group II

Ca + 2 H2O → Ca(OH)2 + H2 (g)

A hydroxide and hydrogen gas are formed
Halogen w/ more active halogen

Replacement of a halogen by a more active halogen

Cl2 + 2 KBr → 2 KCl + Br2

Br2 + 2 KI → 2 KBr + I2

MgBr2 + I2 → no reaction because Br is more active
than I, so I will not replace Br

The corresponding metallic compound and elemental
halogen are formed
P.C.S. Mazintl
P potassium
C calcium
S sodium
M magnesium
a aluminum
z zinc
i iron
n nickel
t tin
l lead
HYDROGEN
Copper
Mercury
Silver
Activity of Halogens
Fluorine
Chlorine
Bromine
Iodine
More Active
Activity Series of the elements

A + BX → AX + B

If A replaces B, then A is more active than B

If an element is above another element on the chart,
then it is more active, and will replace the lower
positioned element

All metals above hydrogen displace hydrogen from
hydrochloric acid or dilute sulfuric acid.
P.C.S. Mazintl
P potassium
C calcium
S sodium
M magnesium
a aluminum
z zinc
i iron
n nickel
t tin
l lead
HYDROGEN
Copper
Mercury
Silver
Activity of Halogens
Fluorine
Chlorine
Bromine
Iodine
More Active
Example

Zn (s) + CuSO4 (aq)→
P.C.S. Mazintl
P potassium
C calcium
S sodium
M magnesium
a aluminum
z zinc
i iron
n nickel
t tin
l lead
HYDROGEN
Copper
Mercury
Silver
Activity of Halogens
Fluorine
Chlorine
Bromine
Iodine
More Active
Example

Zn (s) + CuSO4 (aq)→ ZnSO4 (aq) + Cu (s)

Mg (s) + Zn(NO3)2 (aq) → Mg (NO3)2 (aq) + Zn (s)
Double Replacement

AX + BY → AY + BX

usually takes place in a solution of water

2 compounds → 2 different compounds


1 of these will not be soluble in water
In order for you to know if the reaction has occurred, a solid or gas
must form

1 product will typically be:

solid: precipitate

gas: CO2 SO2 NH3
Solubility Rules for Double
Dis(RE)placement Reactions
How to determine which product is the
precipitate
Na+
Will always be soluble in water.
+
K
Tells you what won’t precipitate, so
NH4+
assume the other one will
NO3
[
Examples

Pb(NO3)2 (aq) + KI (aq) → PbI2 (s)+ 2 KNO3 (aq)
Examples

CaCO3 + 2 HCl → CaCl2 + H2CO3
H2O + CO2

NaOH (aq) + KI (aq) →
NaI (aq) + KOH (aq)
→
no reaction because
both products are
soluble (aq)
Writing Molecular, Complete Ionic,
and Net Ionic Equations (7.7 Tro)

Molecular Equations: an equation
showing the complete neutral formulas for
every compound in the reaction.

AgNO3 (aq) + NaCl (aq)→ AgCl(s) + NaNO3 (aq)
Complete Ionic Equations
equations that show reactants and
products as they are actually present in
solution.
 Ionic compounds dissociate (dissolve) in
water, so they are written as individual
ions…if the compound is soluble…check
your solubility rules


Complete Ionic Equation of:


AgNO3 (aq) + NaCl (aq) → AgCl(s) + NaNO3 (aq)
Spectator Ions:

ions in solution that appear unchanged on
both sides of the equation
Net Ionic Equation:

equations which show only the species
that actually participate in the reaction

Spectator ions are omitted from the net
ionic equation
Net Ionic Equation for:

Ag+ (aq) + NO3- (aq) + Na+ (aq) + Cl- (aq) → AgCl(s) + Na+ (aq) + NO3-(aq)
Write the molecular, complete
ionic and net ionic equations for

lead (II) nitrate reacts with lithium chloride
Write the molecular, complete
ionic and net ionic equations for

Hydrobromic acid reacts with calcium hydroxide
END