Question

Think about the assumptions involved in the ideal gas law and kinetic molecular theory. For each pair below determine which system is more likely to obey the ideal gas law and explain why you made your choice. A one liter container of Xe at 760 torr and 273 K or A one liter container of He at 760 torr and 273 K? A one liter container of He at 76.000 torr and 273 K or A one liter container of He at 760 torr and 273 K?

Answer 1

Kinetic molecular theory assumes that size of the particles or atoms is negligible compared to size of vessel or container in which gas is kept. For the first condition of one liter container of Xe at 760 torr and 273 K or A one liter container of He at 760 torr and 273 K, we can see that temperature and pressure conditions are same. But size of xenon molecule is much bigger than size of a helium molecule. Due to bigger size of molecules of Xenon, its volume is not negligible and will not follow ideal gas law. Hence Helium is more likely to obey the ideal gas law.

Real gases obey ideal gas laws at low pressure and high temperature. For the second condition of one liter container of He at 76.000 torr and 273 K or A one liter container of He at 760 torr and 273 K, the gas which has lower pressure is more likely to obey the gas law. This means He at 76.000 torr and 273 K will obey the ideal gas laws to a higher degree