With prolonged storage in air, 10.36 g of copper powder increased its weight to 11.66 g.

With prolonged storage in air, 10.36 g of copper powder increased its weight to 11.66 g. Since the transformation was complete, what kind of copper oxide was formed?

1. Let’s write down the equation of copper oxidation:

2xCu + O2 = 2CuxO;

2. find the mass of oxygen:

m (O) = m (CuxO) – m (Cu) = 11.66 – 10.36 = 1.3 g;

3.Calculate the chemical amounts of elements in the oxide:

n (Cu) = m (Cu): Ar (Cu) = 10.36: 64 = 0.161875 mol;

n (O) = m (O): Ar (O) = 1.3: 16 = 0.08125 mol;

4.Let’s find the ratio of the amounts of elements in the oxide:

n (Cu): n (O) = 0.161875: 0.08125 = 2: 1.

Answer: Cu2O.