Calculate how many grams of calcium oxide (CaO) is formed when burning a ring weighing 20 grams.

Reaction equation: 2Ca + O2 = 2CaO
Let us find the amount of calcium substance by the formula n = m / M, where M (Ca) = 40 g / mol is the molar mass determined according to the periodic table. n (Ca) = 20 g / 40 g / mol = 0.5 mol.
According to the reaction, 2 mol of oxide is formed from 2 mol of calcium, which means n (Ca) = n (CaO) = 0.5 mol.
The mass is found by the formula: m = n * M. The molar mass of calcium oxide M (CaO) = 40 + 16 = 56 g / mol. m (CaO) = 0.5 mol * 56 g / mol = 28 g.
Answer: 28 g of calcium oxide is formed.