My teacher says the correct way to predict/balance the equation AL+HCL yields H+AlCl3 is to balance it like this: 2Al+6HCl yields 3H2+2AlCl3. I don't get why there is a two in front of the AlCl3. Could you guide me through the logic of this please?

Answer 1

Surely.
You have 2 Al on the left; therefore, there must be a 2 for 2AlCl3 to keep the Al atoms the same on both sides.
Second reason:
There are 6 Cl atoms on the left (from 6HCl) and there must be 6 Cl atoms on the right. A 2 coefficient for 2AlCl3 gives 2 Al and 6 Cl in one swell foop.

Answer 2

I'm still a little unsure in front of the first Al why there's a two. Could you explain?

Answer 3

Since you have the cooefficient of 6 before HCl, you must have 6 Cl atoms on the other side as well.

AlCl3 already has 3 Cl atoms so if you put a 2 as the coefficient that gives you 6 (2 x 3 =6).

You have balanced the Cl atoms but now you have unbalanced Al atoms. If you put a 2 in front of the first Al then it balances.

post if you still don't understand