Calculate the amount of substance that is formed during the combustion of 0.3 mol of calcium.

First, we write down the equation of reactions, and then we equalize.
2Ca + O2 = 2 CaO.
Further, according to the reaction equation, we determine the amount of the formed substance. We write down the solution.
0.3 mol Ca – x mol CaO.
2 mol Ca – 2 mol CaO.
Find the unknown value of x. We write down the solution.
X = 0.3 mol × 2 mol ÷ 2 mol = 0.3 mol CaO.
This means that the amount of the substance of the formed calcium oxide is 0.3 mol.
Answer: n (CaO) = 0.3 mol.