CHEMICAL REACTIONS
The process by which one or more substances are
changed into one or more different substances
Word Equations
 To write a word equation,
Write the names of the reactants to the left of the
arrow separated by plus signs;
2. Write the names of the products to the right of the
arrow, also separated by plus signs.
1.
Reactant + Reactant  Product + Product
EXAMPLE
 Methane + Oxygen  Carbon dioxide + Water
EXAMPLE 2
Iron + Oxygen  Iron(III) Oxide
EXAMPLE 3
Hydrogen Peroxide Water and Oxygen
Skeleton Equations
 Write the formulas of the reactants to the left of the yields
sign (arrow) and the formulas of the products to the right.
 A skeleton equation is a chemical equation that does not
indicate the relative amounts of the reactants and products.
 Here is the equation for rusting:
 Fe + O2  Fe2O3
 Formula Writing Practice WS
Catalyst
 A catalyst is a substance that speeds up the reaction but is
not used up in the reaction
 Without catalyst
With Catalyst
Important Symbols
Balancing Chemical Equations
 To write a balanced chemical equation,
Write the skeleton equation
2. Use coefficients to balance the equation so that it obeys the law
of conservation of mass.
 Remember you want the same number of atoms of each element
on each side of the equation.
1.
Example
Example 2
Example 3 -- Try on your own!!!
 Write a balanced chemical equation for the reaction in which
sodium hydroxide and calcium bromide react to produce
solid calcium hydroxide and sodium bromide. (The reaction
occurs in water.)
NaOH(aq)+CaBr2(aq)
Ca(OH)2(s)+NaBr(aq)
2NaOH(aq)+CaBr2(aq)
Ca(OH)2(s)+2NaBr(aq)
Summary
Write a skeleton
equation
Count atoms
Add/adjust
coefficients
Reduce coefficients
to lowest possible
ratio
Check your work
Warm Up!!
 _____NaClO3 →____ NaCl + __O2
Chemical Equations from Names
 Magnesium and Hydrogen Chloride produce Hydrogen and Magnesium
Chloride
 Calcium Hydroxide and Lithium Chloride produce Lithium Hydroxide
and Calcium Chloride
 Decompose Copper (II) oxide into Copper and Oxygen
 Aluminum and Iron (III) oxide produce iron and aluminum oxide
 combustion of Butane (C4H10) in air to produce carbon dioxide and water
Warm Up
 ___AgNO3 + __Ni  __Ni(NO3)2 + __Ag
The Five Types of Reactions
Synthesis
Combustion
Decomposition
Chemical
Reactions
Double
Replacement
Single
Replacement
Chemistry with
Synthesis Reactions
A + B  AB
1. Synthesis Reactions
(Combination)
 Two or more reactants produce
one product
 Examples:
NH3 + HCl 
NH4Cl
H2 + O2 
H2O

Ag2S
Al + Cl2 
AlCl3
Ag + S
Chemistry with
Decomposition Reactions
AB  A + B
2. Decomposition
 One reactant produces two or
more products
 Examples
Ag2O Ag + O2
PCl5  PCl3 + Cl2
H2O2 H2O + O2
CuO Cu +
O2
Chemistry with
Single Replacement
AB + C  AC + B
3. Single Replacement
 One element replaces another
element
 Must consult the activity series
3. Single Replacement
 One element and one
compound producing a
different element and
compound
 Examples
Fe + H3(PO4)  H2 + Fe3(PO4)2
H2 + CuO  Cu + H2O
Zn + HCl  H2 + ZnCl2
Cl2 + KBr  Br2 + KCl
Equations Activity Series Worksheet
Chemistry with
Double Replacement
AB + CD  AD + CB
4. Double Replacement
A double-replacement reaction is
a chemical change involving an
exchange of positive ions between
two compounds.
 Examples:
Al(NO3)3 + NaOH  Al(OH)3
+ NaNO3
PbCl2 + Li2SO4  PbSO4 +
LiCl
ZnBr2 + AgNO3  Zn(NO3)2
+ AgBr
BaCl2 + KIO3  Ba(IO3)2 +
KCl
4. Double replacement
 Three main products of a double replacement reaction
 Precipitate (solubility table)
 Water
 Gas
5. Combustion
 A combustion reaction
 Chemical change
 Element or a compound reacts with oxygen
 Producing energy in the form of heat and light
5. Combustion
A hydrocarbon reacts with oxygen to produce carbon dioxide
and water
Examples:
CH4 + O2  CO2 + H2O
C6H12O6 + O2  CO2 + H2O