When copper (II) oxide was dissolved in excess sulfuric acid, a salt of 40 g was formed. The mass of copper (II) oxide was

Reaction equation:

CuO + H2SO4 = CuSO4 + H2O

From the reaction equation, we can conclude that the salt formed is copper sulfate. We calculate its amount of substance:

n (CuSO4) = m (CuSO4) / M (CuSO4) = 40/160 = 0.25 mol.

In the reaction equation, copper oxide and copper sulfate have the same coefficients. This means that their amounts of substance are also equal, i.e.:

n (CuO) = n (CuSO4) = 0.25 mol

Therefore, the mass of copper oxide is equal to:

m (CuO) = n (CuO) ⋅ M (CuO) = 0.25 ⋅ 80 = 20 g.

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