Q.Gases tend to behave ideally only at:

For an ideal gas, the compressibility factor Z = 1.

The compressibility factor is defined as Z = PV / nRT. Since an ideal gas obeys PV = nRT exactly at all conditions, substituting gives Z = nRT / nRT = 1. Any deviation o …

Real gases behave most ideally at high temperature and low pressure, where intermolecular attractions and the finite size of molecules both become negligible.

The ideal gas equation PV = nRT assumes that gas molecules have no volume of their own and exert no attractive or repulsive forces on each other. Real gases deviate from this because of (i) intermolecular attractive forces, which pull molecules together and reduce the pressure they would otherwise exert, and (ii) the actual finite volume occupied by the gas molecules themselves.

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