Balancing Chemical Equations
Statement in which chemical formulas are used to
describe a chemical reaction.
Chemical Equation:
____Reactants___________ ------- ____Products__________
- start with
- what is changed during a
chemical reaction
-end with
-different physical and
chemical properties from
reactants
The left side of an equation contains the __reactants___ for a chemical reaction.
In a reaction the arrow always points to the __products__ of a chemical reaction.
In the following equations, circle the reactants and underline the products:
2KClO3  2KCl + 3 O2
3H2O + 2Fe  Fe2O3 + 3H2
Na2O + CO2  Na2CO3
The Law of Conservation of __Matter____________:
Since matter can NOT be lost or destroyed, the kind of atoms and the _number_
of each kind of atom must be the same on both sides of the chemical equation.
The number of atoms in the _reactants___will always equal the
number of atoms in the _products______.
The coefficient is the number written in __front____ of the chemical formula.
The coefficient shows how many _molecules___ of a substance are involved in a
chemical reaction.
1. Underline each subscript twice.
2. Put a box around each coefficient.
3. Calculate the total number of atoms of each element in the compound.
Total number of atoms of an element = coefficient X subscript
3 Na2O
5 H2SO4
Na sodium = 3 X 2 = 6 _ H hydrogen = 5 X 2 =10__________
O = oxygen 3 X 1 = 3
S sulfur= 5 X 1 = 5 __
O oxygen = 5 X 4 = 20 _
To balance the equation only the ________Coefficient____ can be changed.
1. ______H2 +______O2 --------- ______ H2O
H hydrogen 1 X 2 = 2
H hydrogen 1 X 2 = 2
O oxygen 1 X 2 = 2
O oxygen 1 X 1 = 1
2. ______Mg + ______ HCl --------- ______MgCl2 + _____H2
Mg Magnesium 1 X 1 = 1
Mg Magnesium 1 X 1 = 1
H hydrogen 1 X 1 = 1
Hydrogen = 1 X 2 = 2
Cl chlorine 1 X 1 = 1
Cl chlorine 1 X 2 = 2
3. _____H2O + _____Fe --------- _____Fe2O3 + _____H2
H hydrogen 1 X 2 = 2
H Hydrogen 1 X 2 = 2
O oxygen 1 X 1 = 1
O oxygen
1X3=3
Fe iron 1 X 1 = 1
Fe iron
1X2=2