How many moles of aluminum oxide are in a sample with a mass of 204

(204 g) / (101.96 g/mol) = 2.001 mol. 2 (2.001) = 4.002 moles of aluminium in the sample

Answer: 108 g

Explanation:

The molar mass of aluminium is 26.98 g/mol; the molar mass of (atomic) oxygen is 16.00 g/mol.

1 mole of Al₂O₃ therefore has a mass of 2 (26.98) + 3 (16.00) = 101.96 g.

Divide this into the given mass, to find the number of moles here:

(204 g) / (101.96 g/mol) = 2.001 mol.

There are 2 moles of aluminium per mole of aluminium oxide, so there are

2 (2.001) = 4.002 moles of aluminium in the sample.

Then there are (4.002 mol) (26.98 g/mol) = 107.97 g of Al. Since the given mass has only 3 significant figures, round this answer to 108 g.