Balancing Chemical Equations

What is a Chemical Equation?• When a chemical reaction

occurs, it can be described by an equation.

• This shows the chemicals that react (called the reactants) on the left-hand side, and the chemicals that they produce (called the products) on the right-hand side.

• The chemicals can be represented by their names or by their chemical symbols.

• Unlike mathematical equations, the two sides are separated by an arrow, that indicates that the reactants form the products

The Concept of Balancing Equations

• Take a look at this chemical word equation: Aluminum + Oxygen Aluminum Oxide

• This is the equation for the burning of aluminum in oxygen.

• If we convert each of the chemical names into the appropriate symbols, we get the following:

Al + O2 Al2O3

The Concept of Balancing Equations

Al + O2 Al2O3

• You can see by looking at it that there is something wrong with this equation. If you count the number of atoms of each type on each side, you will see that there is only one aluminum atom on the left side whereas there are two on the right. There are two oxygen atoms on the left side, as compared to three on the right side. This clearly doesn't match.

• Left side:              Right side:

The Rules of Balancing Equations

1. Split the equation into a reactants side and a products side by drawing a line down the center of the arrow

Al + O2 Al2O3

Reactant side Product side

The Rules of Balancing Equations

2. Take an atom inventory on each side of the equation – make sure to count the TOTAL number of atoms!

Al + O2 Al2O3

Al 1

O 2

Al 2

O 3

The Rules of Balancing Equations

3. Balance the atoms on each side of the equation using COEFFICIENTS

__Al + __O2 __Al2O3

Al

O

Al

O

1 4

2 6

2 4

3 6