Lab book page: ____
Balancing Chemical Equations
Steps for Balancing Chemical Equations:
1. Set up REP (Reactants, Elements, Products) table.
2. Put boxes around all molecules in the chemical equation. You can’t change subscripts.
3. Fill in the elements column of the REP table.
4. Fill in the number of atoms for each element in the REP table for the reactants and
products assuming coefficients are 1.
5. Identify element(s) that are not balanced.
6. Identify the side (reactants or products) that needs to be balanced. It will be the lower
number.
7. Find which coefficient will balance the side of the chemical reaction. Remember, the
coefficient is at the front of the molecule. You can’t change subscripts.
8. Adjust the number of atoms in the REP table.
9. Repeat steps 5-8 until all atoms are balanced.
In a balanced chemical equation, the number of atoms for each element of the reactants must be
equal to the number of atoms for each element of the products.
**Subscripts are the number of atoms of the preceding element only.
** Coefficients are the number of molecules/compounds.
Examples:
H2
= two hydrogen atoms
4NaCl = four molecules of Sodium Chloride giving 4 Na atoms and 4 Cl atoms
2H2 = two molecules of H giving four atoms of H
Reactant + Reactant
Product +
Product
Example:
Zn
+ CuSO4
Cu
+
Symbol
ZnSO4
Name
What are the reactants?
What are the products?
Reactants
Elements
Products
Zn
Cu
S
O
1
Lab book page: ____
Example 1:
Balance the following equations:
Rewrite the equation underneath
the original.
1. H2
+
O2
Reactants
Element
Products
O
H
H2O
Example 2: Balance the following equations:
Rewrite the equation underneath the original.
2.
3.
4.
5.
6.
Mg
+
CH4
+
H2CO3
O2
+
KClO3
Na
+
O2
MgO
CO2 +
Ca(OH)2
CaCO3
KCl
Cl2
H2 O
+
+
H2O
O2
NaCl
2