Find the Mass of Oxygen Containing 12 * 10 ^ 24 Molecules

Let’s write an expression to determine the amount of a substance:
ν = m / M = N / Na, where m is the mass of the substance, M is the molar mass of the substance, N is the number of particles, Na is Avogadro’s constant Na = 6.023 * 10 ^ 23 1 / mol.
Let us express the mass of oxygen from this expression:
m = N * M / Nа
The molar mass of oxygen M (O2) = 2 * 0.016 = 0.032 kg / mol.
Substitute the numerical values:
m = N * M / Na = 12 * 10 ^ 24 * 0.032 / 6.023 * 10 ^ 23 = 0.64 kg.
Answer: the mass of oxygen is 0.64 kg.