Question

which of the following statements is incorrect?deviations from ideal gas behaviour are most significant at very high temperatures.for real gases, the observed pressure of a gas is usually lower than the pressure predicted by using the ideal gas equation.for an ideal gas the compressibility factor, z

Answer 1

The first statement is most likely wrong.
An ideal gas follows one of its assumptions that it has no intermolecular forces of attraction. At high temperatures, the molecules have enough energy to overcome the intermolecular forces of attraction between the molecules. Hence, deviation from ideal gas behaviour reduces as temperatures rise.
As a side note lowering the pressure would also reduce the deviation of ideal gas behaviour as the other assumption of an ideal gas is that the volume of the particles have negligible volumes compared to the container it is stored in. At low pressures the particles are far apart from one another, hence they have increasingly negligible volume as the pressure falls.