0.2 mol of oxygen uses 0.2 mol of calcium to burn. Determine the amount of calcium oxide?

The reaction of calcium proceeds with oxygen according to the scheme:

2Ca + O2 = 2CaO

The reaction coefficients mean that the oxidation of 2 mol of calcium (Ca) requires 1 mol of oxygen (O2). Accordingly, 0.2 mol of calcium will require only 0.1 mol of oxygen for combustion; the reaction is carried out under conditions of an excess of an oxidizing agent.
As a result, 0.2 mol of calcium oxide (CaO) is formed and 0.1 mol of oxygen remains unused. We calculate the mass of the formed calcium oxide using the equation:

m = n * M,

where M is the molar mass of calcium oxide

M = 40.1 + 16.0 = 56.1 [g / mol],
m = 0.2 * 56.1 = 11.2 [g].

Thus, when burned, we get 0.2 mol of calcium oxide (CaO) with a mass of 11.2 g.