Greetings!
When balancing an equation, you need to know how many of each atom is on each side.
Left hand side:
1 Al , 1H , 1 Cl
Right hand side:
1 Al , 3 Cl, 2 H
You need to change the numbers on each side until the same amount is on both sides:
Al + HCl → AlC₃ + H₂
Al + 3HCl → AlC₃ + H₂
Al + 3HCl → AlC₃ + 3H₂
Al + 3HCl → AlC₃ + 3H₂
Al + 6HCl → AlC₃ + 3H₂
Al + 6HCl → 2AlC₃ + 3H₂
2Al + 6HCl → 2AlC₃ + 3H₂
Which is now balanced!
The balanced equation again is:
2Al + 6HCl → 2AlC₃ + 3H₂
Hope this helps!
