By burning 128 g of copper, copper oxide CuO was obtained. Find the mass of the oxide.

Let’s find the amount of substance CuO.

n = m: M.

M (Cu) = 64 g / mol.

n = 128 g: 64 g / mol = 2 mol.

Let’s compose the reaction equation. Let’s find the quantitative ratios of substances.

2Cu + O2 = 2CuO.

According to the reaction equation, 2 mol of Cu accounts for 2 mol of CuO.

Substances are in quantitative ratios 1: 1.

n (Cu) = n (CuO) = 2 mol.

Let’s find the mass of CuO.

M (CuO) = 80 g / mol.

m = n × M.

m = 80 g / mol × 2 mol = 160 g.

Answer: 160 BC