States of matter: describe question

A sample of nitrogen, $\ce{N2}$, is compressed in a sealed cylinder to a very high pressure. At this pressure the gas does not behave as an ideal gas: its measured volume is greater than the value predicted for an ideal gas, and its measured pressure is lower than the predicted value.

(a) Describe how the nitrogen molecules exert a pressure on the walls of the cylinder.

(b) Describe the two assumptions made about the molecules of an ideal gas, and describe how the failure of each assumption at high pressure accounts for the observed deviations from ideal behaviour.