Question

What types of conditions are considered non-ideal ?
(A) Very high densities
(B) Very high pressure
(C) Very low volume
(D) Very low temperature
(E) All the above

Answer 1

An ideal gas is a theoretical gas made up of a large number of randomly moving point particles with no interparticle interactions. Because it obeys the ideal gas law, a simplified equation of state, and is susceptible to statistical mechanics analysis, the ideal gas notion is helpful. If the interaction is fully elastic or viewed as point-like collisions, the criterion of zero interaction can frequently be waived.

Complete answer:
When intermolecular interactions and molecular size become relevant at lower temperatures or greater pressures, the ideal gas model tends to collapse. Most heavy gases, such as many refrigerants, and gases with high intermolecular interactions, such as water vapour, fail to pass this test. The volume of a real gas is typically much bigger than that of an ideal gas at high pressures. A real gas's pressure is frequently lower than that of an ideal gas at low temperatures. Real gases undergo a phase transformation, such as to a liquid or a solid, at a low temperature and high pressure. The ideal gas model, on the other hand, does not describe or enable phase transitions. More complicated state equations must be used to represent them. The compressibility factor, Z, describes the departure from ideal gas behaviour. In both Newtonian and quantum mechanics, the ideal gas model has been investigated. The ideal gas model, which is one of the most important in statistical mechanics, has also been used to simulate the behaviour of electrons in a metal. 'Non-ideal' conditions include extremely high densities, extremely high pressures, extremely small volumes, and extremely low temperatures. The 'optimal' conditions are moderate densities, moderate pressures, moderate volumes, and moderate temperatures.
Hence option E is correct.

Note:
The temperature of an ideal gas does not change as the pressure is dropped in a throttling operation. (Depending on whether an actual gas's Joule–Thomson coefficient is positive or negative, its temperature falls or increases when its pressure is decreased in a throttling operation.)