Question

when 2.50grams of copper(Cu) reacts with oxygen, the copper oxide product has a mass of 2.81grams. what is the simplest formula of the copper oxide?

Answer 1

The number of moles of 'Cu' present = Wt/Molar mass
=2.50 g / 63.546 g/mol
=0.03934 mol
If all 'Cu' converted to the cupper oxide then, the samenumber of moels of cu present in the product.
Therefore mass of 'Cu' present in the product = 2.50 g
Therefore mass of the oxygen = 2.81 g - 2.50 g
=0.31 g
Thus the number of moles of 'O' in the product = 0.31g/16.0g/mol
=0.019325 mol
Therefore
CuO
0.03934mol0.019325mol
0.03934/0.0193250.019325/0.019325
21
Therefore Empirical formula of the product = Cu₂O