Calculate how many molecules 64 grams of oxygen contain.

The number of oxygen molecules is calculated by the following formula
N = m * Na / M
Where N is the number of molecules of the substance, m is the mass of the substance, Na is Avogardo’s constant, which is 6.02 × 10 ^ 23, M is the molar mass of water.
The mass of oxygen is given, it is equal to 64 g, which is converted into kilograms. There are 1000 grams in one kilogram, which means the mass of oxygen is 64 ÷ 1000 = 0.064 kg.
Further, the molar mass of oxygen is 0.064 kg / mol.
We substitute in the formula and solve:
N = 0.064 × 6.02 × 10 ^ 23 / 0.064 = 6.02 × 10 ^ 23
Answer: 6.02 × 10 ^ 23 oxygen molecules.