Ideal Gas Laws and Real Gases

The ideal gas law is a fundamental concept in thermodynamics that describes the behavior of gases under different conditions. However, real gases do not always behave ideally under all conditions. At low pressures and high temperatures, most gases follow the ideal gas law closely, but as the pressure increases or the temperature decreases, real gases begin to deviate from ideal gas behavior.

The Critical Temperature

The temperature at which a real gas can be compressed to a liquid state is called the critical temperature. Above this temperature, the gas cannot be liquefied, no matter how much pressure is applied. At the critical temperature, the gas has a very low compressibility factor, which means that it behaves more like an ideal gas.

The Reduced Temperature

The reduced temperature is a dimensionless quantity that is used to determine whether a gas will behave ideally or not. The reduced temperature is defined as the ratio of the gas temperature to its critical temperature. If the reduced temperature is greater than 1, the gas will not behave ideally and will exhibit significant deviations from the ideal gas law.

The Reduced Pressure

The reduced pressure is another dimensionless quantity that is used to determine whether a gas will behave ideally or not. The reduced pressure is defined as the ratio of the gas pressure to its critical pressure. If the reduced pressure is less than 0.3, the gas will behave ideally over a wide range of pressures.

Conclusion

In conclusion, the temperature at which real gases obey ideal gas laws over an appreciable range of pressure is the critical temperature. However, the behavior of real gases can also be determined by the reduced temperature and reduced pressure. Understanding these concepts is crucial for predicting the behavior of real gases under different conditions.

Boyle's temperature