Question

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?

Answer 1

The balance chemical reaction is
2Al + 6HCl  -à 2AlCl3 + 3H2 A
ssuming excess amount of HCl because it is not given  
Mole Al reacted = 13.5 g ( 1 mole/ 27 g)
= 0.5 mole Al  

Mole H2 = 0.5 mol Al ( 3 mole H2 / 2 mole Al)  =
0.75 mole H2  

since at STP then 1 mole gas occupies 22.414 L
volume H2 = 0.75 mole (22.414 L / mol)
= 16.8105 L H2

Answer 2

Answer:

1) 0.5 mol.

2) 0.75 mol.

3) 16.8 L.

Explanation:

1) How many moles of Al react?

• We can calculate the number of moles of Al (n) using the relation:

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?

• It is a stichiometry problem.

• We should write the balanced equation of the reaction:

2Al + 6HCl → 2AlCl₃ + 3H₂.

• It is clear that 2.0 moles of Al reacts with 6.0 moles of HCl to produce 2.0 moles of AlCl₃ and 3.0 moles of H₂.

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.