When 6.0 mol H2O reacts with 5.0 mol Al in the reaction below, 4.0 mol of Al are used up in the reaction. How many moles of Al are left over unreacted?

Reaction: 2Al + 3H2O → Al2O3 + 3H2

1 mole

Explanation:

Given parameters:

number of moles of H₂O = 6moles

Number of moles of Al used up = 4 moles

Number of moles of Al given = 5 moles

Unknown:

Number of moles of Al left unreacted = ?

Solution

To solve this problem, we are going to use the mole approach. The balanced chemical equation furnishes us with an overview of the amount of reactants used in the reaction.

The balanced equation is shown below:

2Al + 3H₂O → Al₂O₃ + 3H₂

we can also see that 4 moles of aluminium was used up in the reaction.

The amount of unreacted aluminum = Number of moles given - number of moles used

= 5 mole - 4 mole

= 1 mole