**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 + I_{2} –> (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 + I_{2} –> 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 I_{3} (aluminum iodide).

Al + I_{2} –> Al I_{3}

**3.** **Balance the equation.**

Al + I_{2} –> Al I_{3}

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 + **3**I_{2} –> **2**Al I_{3}

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

**2**Al + **3**I_{2} –> **2**Al I_{3}

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

**Answer to Problem:** **2Al + 3I _{2} –> 2AlI_{3}**

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