Determine the density of oxygen at 100 ° C and a pressure of 2 * 10 ^ 5 Pa.

Ideal gas equation of state (Mendeleev – Clapeyron equation):
Р * V = (m / M) * R * T, where Р – gas pressure (2 * 10 ^ 5 Pa), V – gas volume, m – gas mass, M – molar mass (0.032 kg / mol), R – Boltzmann constant (8.31 J / (mol * K)), T – absolute temperature (100 C = 373 K).
By converting:
(P * M) / (R * T) = m / V, where m / V = r (density).
r = ((2 * 10 ^ 5) * 0.032) / (8.31 * 373) = 2.065 kg / m ^ 3.
Answer: the oxygen density will be 2.065 kg / m ^ 3.