Download rules for balancing chemical equations

MR. SCHLESINGER’S RULES FOR BALANCING
CHEMICAL EQUATIONS
You must never forget:

In most chemical reactions, two or more substances, called reactants, interact to create different
substances called products. The reactants are always on the LEFT of the reaction arrow; the
products are to the RIGHT of the reaction arrow.

The little numbers are called subscripts. NEVER CHANGE THE SUBSCRIPTS!

Due to the law of conservation of matter, the reactants MUST contain the same elements
and the same number of each element as the products. However, they CAN be in different
compounds. When the number of each element/ion is the same on both sides, the
equation is balanced.
To balance a chemical equation:
1. COUNT the total number of atoms/ions of each element in the reactants and the total number of
atoms/ions of each element in the products. You must make a RAP table when balancing. A
RAP chart for the example chemical equation (above) would look like this:
** VERY IMPORTANT: A polyatomic ion that appears unchanged on both sides of th equation is
counted as a single unit.
**VERY IMPORTANT: If there is a subscript outside of parenthesis, we distribute the subscript to
each element inside of the parenthesis. Example:
(OH)2
=
(OH)2 =
2 OXYGEN ATOMS + 2 HYDROGEN ATOMS
2. Balance the elements one at a time using coefficients.
A coefficient is a small WHOLE number that is written in front
of a chemical formula in a chemical equation. Note: When no coefficient is written,
the coefficient is assumed to be 1.
Pro Tip: It is best to begin with elements OTHER THAN hydrogen and oxygen. These elements
often occur more than twice in equations.
** You must NEVER!!!!!! attempt to balance the equation by changing subscripts in chemical
formulas!!!!!! NEVER!!!!!!!
3.
CHECK each atom/ion, or polyatomic ion to be sure that the equation is correctly balanced.
4. Finally, make sure that all of the coefficients are in the LOWEST possible whole number ratios.
Examples:
1. UNBALANCED:
____H2 + ____O2 →
___H2O
Balanced:
2. UNBALANCED: ____ N2 + ____ H2 → ____ NH3
Balanced:
3. UNBALANCED: ____ Pb(OH)2 + ____ HCl → ____ H2O + ____ PbCl2
Balanced: