At what pressure can you use the ideal gas law to find the density of a gas?

The ideal gas law, expressed as PV = nRT or rearranged to find density (ρ = PM/RT), provides a useful approximation for determining the density of a gas under certain conditions. The ideal gas law assumes that the gas behaves ideally, which generally occurs at low pressures and high temperatures. Under these conditions, gas molecules are relatively far apart, and interactions between them are minimal, allowing the equations to accurately represent their behavior.

At pressures lower than 3 atm, gases are more likely to behave ideally because the intermolecular forces have less effect on the gas particles. As the pressure increases beyond this threshold, especially if approaching higher pressures, real gases begin to deviate from ideal behavior due to increased interactions between gas particles and a possible increase in condensation effects.

Therefore, using the ideal gas law is most reliable when the gas is at pressures below 3 atm, making it the appropriate choice for calculating density in a range of realistic scenarios.