Determine the number of molecules in 1 m ^ 3 oxygen.

N = υ * Na, where υ is the amount of substance (mol), Na is Avogadro’s number (Na = 6 * 10 ^ 23 mol-1).
Amount of substance:
υ = m / M, where m is the mass of oxygen (m = ρ * V, ρ is the oxygen density (ρ = 1.43 kg / m3), V is the volume occupied by oxygen (V = 1 m3)), M is the molar mass oxygen (diatomic gas, M = 32 g / mol = 0.032 kg / mol).
Number of molecules:
N = υ * Na = ρ * V * Na / M = (1.43 * 1 * 6 * 10 ^ 23) / 0.032 = 268.125 * 10 ^ 23.
Answer: The number of molecules in 1 m3 of oxygen is 268.125 * 10 ^ 23.