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Concord High School Chemistry

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Practice Problem #3:

aluminum + iodine –>

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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