Assume that 13.5 g solid aluminum (al) react with hcl to produce solid aluminum chloride (alcl3) salt and gaseous hydrogen (h2) at standard temperature and pressure.
how many moles of al react?
how many moles of h2 are produced?
how many liters of h2 are produced?

1) 0.5 mol.

2) 0.75 mol.

3) 16.8 L.

Explanation:

1) How many moles of Al react?

n = mass / molar mass,

Mass of Al = 13.5 g.

Molar mass mass of Al = 26.98 g/mol.

∴ The number of moles of Al (n) = mass / molar mass = (13.5 g) / (26.98 g/mol) = 0.5 mol.

2) How many moles of H₂ are produced?

2Al + 6HCl → 2AlCl₃ + 3H₂.

Using the cross multiplication:

2.0 moles of Al → 3.0 moles of H₂, from the stichiometry,

0.5 mole of Al → ??? moles of H₂.

∴ The number of moles of H₂ are produced = (0.5 mole)(3.0 mole) / (2.0 mole) = 0.75 mol.

3) How many liters of H₂ are produced?

It is known that at STP, 1.0 mole of any gas occupies a volume of 22.4 L.

Using cross multiplication:

1.0 mole occupies → 22.4 L.

0.75 mole occupies → ??? L.

∴The number of liters of H₂ are produced = (0.75 mole)(22.4 L) / (1.0 mole) = 16.8 L.