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This page was last updated on
15Jun02
Balancing Equations
Here's a great method to help you balance equations in Chemistry. It's not the quickest method, but it makes understanding the process easier, and helps you doublecheck your answers.
Let's use the following reaction as our sample problem:
Unbalanced Equation
You need to make both sides equal for the equation to be valid. Right now, the sides are not equal.
Make a table with two columns. List the elements in both sides of the equation down the side, then note how many atoms of each element are on each side:

Side 1 of the Equation

Side 2 of the Equation

Aluminum

2

1

Oxygen

3

1

Carbon

1

1

On the first side, you have 2 aluminums, 3 oxygens and 1 carbon. On the other side, you have one each of aluminum, carbon and oxygen. You need both sides to have the SAME number of each element.
Let's start by doubling the number of aluminum atoms on the second side of the equation (you can pick any element to start with...I just picked aluminum because it is alone on the second side, and easier to work with):
Now we have two aluminum atoms on both sides. The aluminums balance. Next, we can multiply the CO compound on the second side by 3:
Al2O3 + C > 2Al + 3(CO)

Now we have three oxygen atoms on each side of the equation, so they are equal. (Note that when you multiply the oxygen on the second side by 3, you are also multiplying the carbon atom by 3 also, since they are a compound).
OK, we have 2 aluminums on each side, three oxygens on each side, and the final element is carbon, which remains unbalanced. We have 1 carbon on the first side and 3 on the second side. We can multiply the carbon atom on the first side by three to complete the balancing:
Balanced Equation
Al2O3 + 3C > 2Al + 3CO

All the elements are present in equal amounts on both sides of the equation now.

Side 1 of the Equation

Side 2 of the Equation

Aluminum

2

2

Oxygen

3

3

Carbon

3

3

That's all there is to it! It does get more tricky, but if you use the table method, you will be able to keep track of what is going where, and be able to check your work.
Periodic Table of Elements
Click on an element in the chart to see its name, atomic number, atomic mass, boiling point and melting point.
Periodic Table of the Elements
Legend 
Metals 
A solid substance that is a good conductor of heat and electricity. Can be formed into many shapes. 
Metalloid 
"Middle elements"  conduct heat and electricity better than nonmetals, but not as well as metals. Easier to shape than nonmetals, but not as easy as metals. Solid at room temperature. 
Nonmetals 
A poor conductor of heat and electricity. Not easily formed into shapes. 
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