How do you balance the equation #Al + HCl -> AlCl_3 + H2#?
You balance it stoichiometrically.
This is NOT the stoichiometric equation:
How would you modify it so that the left had side is equivalent to the right hand side? You can certainly use half-coeffcients,
There are 3 Cl atoms on the product side and 1 on the reactant side. Add a coefficient of 3 in front of
There are now 3 Cl atoms on both sides.
There are 3 H atoms on the reactant side and 2 on the product side. 3 and 2 are multiples of 6. So change the coefficient in front of HCl from 3 to 6, and add a coefficient of 3 in front of the
There are now 6 H atoms on both sides.
Go back to the Cl. There are now 6 Cl on the reactant side and 3 on the product side. Add a coefficient of 2 in front of
There are now 6 Cl atoms on both sides.
Balance the Al
There is 1 Al on the reactant side and 2 Al on the product side. Add a coefficient in front of Al on the reactant side.
There are now 2 Al on both sides and the equation is balanced.