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What is a chemical formula?
View examples of chemical formulas.
What is a coefficient?
What is a subscript?
Differentiate between a subscript and a coefficient in a
chemical formula.
Identify reactants and products in a chemical
equation?
Identify and count the number of atoms in a chemical
equation.
Define the law of conservation of mass.
Observe examples balanced chemical equations.
Balance chemical equations.

Chemical symbols are representations of
elements on the periodic table.

A chemical formula shows the elements
that make up the compound and the
number of atoms of each element in
that compound.
CO2
CO
H2 O
NaCl
H3O
Chemical Formula
H is the symbol
for Hydrogen
O is the symbol
for Oxygen
H 2O
The subscript
means the
molecule of water
has two atoms of
hydrogen
No subscript after
oxygen means the
molecule of water
has only one atom of
oxygen.
Coefficient
Molecule
of Water
3H2O
The coefficient shows the number
of molecules of the compound.
Identify the coefficient and or subscript.
3.
1.
4.
2MgO2
H2O
2AgNO3
3AgNO3
2.
5.
6.
2KOH
CO2

A chemical equation is a representation of a
chemical reaction on paper.

2H2 + O2

CaO + H2O
Ca(OH)2
C
CO2

+ O2
2H2O




Chemical equations area split up into two
parts:
Reactants-the starting materials on the left side
of the arrow
Products-the new substance or substances
produced on the right side of the arrow.
Reactants
Products
C
+O
2
yields
or
produces
REACTANTS
are the starting
materials on
the left side of
the arrow.
CO2
PRODUCT
is the new
substance or
substances
produced and are
on the right side
of the arrow.

Identify the reactants and products.
1.
CH4 + O2
2.
3H2 + N2
3.
2H2 + O2
4.
CaO + H2O
CO2 + 2H2O
2NH3
2H2O
Ca(OH)2

Count the number of atoms in the chemical
equation.
C + O2
CO2

How many carbon (C) atoms on each side?

How many oxygen (O) atoms on each
side?


Count the number of atoms in the chemical
equation.
3H2 + N2
2NH3

How many hydrogen (H) atoms on each side?

How many Nitrogen (N) atoms on each side?


Count the number of atoms in the chemical
equation.
2H2 + O2
2H2O

How many hydrogen (H) atoms on each side?

How many carbon (C) atoms on each side?


Count the number of atoms in the chemical
equation.
2Mg + O2
2MgO

How many magnesium (Mg) atoms on each side?

How many oxygen (O) atoms on each side?


Identify and count the number of atoms in the
chemical equations.
1.
CH4 + 2O2
CO2 + 2H2O
2.
4Al + 3O2
2Al2O3
3.
2K + 2H2O
2KOH + H2



Mass (atoms) cannot be created nor destroyed
in a chemical reaction.
What does that mean for us?
There must be the same number and kinds of
atoms on each side of the chemical equation.
4 P + 5 O2
4 atoms of P
10 atoms of O
=
P4O10
4 atoms of P
10 atoms of O
balanced
H + O2  H2O
H =1
O =2
atom
atoms
=
H =2
O =1
atoms
atom
4H + O2  2 H2O
H =4
atom
O =2
atoms
=
H =4
O =2
atoms
atoms
2
Mg +
O2 
Mg = 2
1
O=
2
2
Mg = 2
1
O= 2
1
MgO
2
Ca +
O2 
Ca = 2
1
O=
2
2
Ca = 2
1
O= 2
1
CaO
N2 +
3
H2 
2
N=
2
2
N= 1
H=
2
6
H=6
3
NH3
2
Cu2O +
C  4 Cu+ CO2
Cu = 4
2
Cu = 1
4
O = 21
O=2
C= 1
C= 1
2
H2O2 
2
H2O +
H=
4
2
H = 42
O=
2
4
O = 43
O2
1.
2.
3.
?
Mg + O2
?
MgO
?
H2 + N2
?
NH3
CH4 +
?
O2
CO2+
?
H20