Problem 4 - Entrance Test

A real gas deviates from ideal behavior primarily due to which of the following reasons? (i) Intermolecular forces of attraction (ii) Finite volume occupied by gas molecules (iii) High kinetic energy of molecules (iv) Negligible volume of molecules compared to container volume

A. (i) and (ii)B. (i) and (iii)C. (ii) and (iv)D. (iii) and (iv)

Correct: A

The ideal gas law is based on two main assumptions: (1) gas molecules have negligible volume compared to the container volume, and (2) there are no intermolecular forces between gas molecules. Real gases deviate from ideal behavior because, in reality, gas molecules do occupy a finite volume (accounted for by the 'b' parameter in the Van der Waals equation) and there are attractive and repulsive forces between them (accounted for by the 'a' parameter). High kinetic energy (iii) actually promotes ideal behavior by helping molecules overcome attractive forces, and negligible volume (iv) is an ideal assumption, not a cause of deviation. Thus, the primary reasons for deviation are (i) and (ii).