Concord High School Chemistry

Balancing Equations Online Help

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Practice Problem #3:

aluminum + iodine –>

Answer to Practice Problem #3:

aluminum + iodine –>

Al + I2 –>                   (remember iodine is diatomic)

1. Identify the type of reaction.

            Synthesis reaction.

            Al combines with I

2. Write out the products of the chemical reaction.

Al + I2 –>  Al I          

(I’ve spaced them so you can see the difference between the “l” in Al and the “I” in iodine)

            Then write the formulas of the products based on their charges.

            Al = +3, I = -1, so the formula is Al I3 (aluminum iodide).

Al + I2 –>  Al I3

3. Balance the equation.

Al + I2 –>  Al I3

            The number of Al atoms is equal on both sides (both have 1).

            Next, there are 2 I atoms on the left and 3 on the right, so balance.

Al + 3I2 –>  2Al I3

            But, that changes it so there are 1 Al atom on the left and 2 on the right, so balance.

2Al + 3I2 –>  2Al I3

            Last, double check that all numbers of atoms of each element is equal.

Answer to Problem: 2Al + 3I2 –>  2AlI3


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