The mass of calcium oxide with a chemical amount of 0.8 mol is equal to.

Find the molar mass of calcium oxide:

M (CaO) = M (Ca) + M (O) = 40 g / mol + 16 g / mol = 56 g / mol (the molar masses of Ca and O numerically coincide with the relative atomic masses of the named elements, their value is indicated in the Periodic Table chemical elements).

The mass of a substance (m) is calculated as the product of its molar mass (M) and the amount (n).

m (CaO) = M (CaO) × n (CaO) = 56 g / mol × 0.8 mol = 44.8 (g)