How would you balance the following equation: aluminum iodide and chlorine gas react to form aluminum chloride and iodine gas?

1 Answer
Dec 16, 2015

Aluminum has a common oxidation state of 3+, and that of iodine is 1-. So, three iodides can bond with one aluminum. You get AlI3.

For similar reasons, aluminum chloride is AlCl3.

Chlorine and iodine both exist naturally (in their elemental states) as diatomic elements, so they are Cl2(g) and I2(g), respectively. Although I would expect iodine to be a solid...

Overall we get:

2AlI3(aq)+3Cl2(g)2AlCl3(aq)+3I2(g)

Knowing that there were two chlorines on the left, I just found the common multiple of 2 and 3 to be 6, and doubled the AlCl3 on the right.

Naturally, now we have two Al on the right, so I doubled the AlI3 on the left. Thus, I have 6 I on the left, and I had to triple I2 on the right.

We should note, though, that aluminum iodide is violently reactive in water unless it's a hexahydrate. So, it's probably the anhydrous version dissolved in water, and the amount of heat produced might explain why iodine is a gaseous product, and not a solid.