_AI + _HCI —> _H2 + _AlCl3

Hey there!

Al + HCl → H₂ + AlCl₃

Balance Cl.

1 on the left, 3 on the right. Add a coefficient of 3 in front of HCl.

Al + 3HCl → H₂ + AlCl₃

Balance H.

3 on the left, 2 on the right. We have to start by multiplying everything else by 2.

2Al + 3HCl → 2H₂ + 2AlCl₃

Now we have 2 on the right and 4 on the left. Change the coefficient in front of HCl from 3 to 4.

2Al + 4HCl → 2H₂ + 2AlCl₃

Now, for Cl, we have 4 on the left and 6 on the right. Change the coefficient in front of HCl again from 4 to 6.

2Al + 6HCl → 2H₂ + 2AlCl₃

Now, our H is unbalanced again. 6 on the left, 4 on the right. Change the coefficient in front of H₂ from 2 to 3.

2Al + 6HCl → 3H₂ + 2AlCl₃  

Balance Al.

2 on the left, 2 on the right. Already balanced.

Here is our final balanced equation:

2Al + 6HCl → 3H₂ + 2AlCl₃  

Hope this helps!

there are two significant figures.