Which of the following diagrams (Fig. 13.5) depicts ideal gas behaviour?

By Ideal Gas equation,

where P, V and T are the pressure, volume and absolute temperature; n is the number of moles of gas; R is the ideal gas constant.

In figure 1, V and T are directly proportional when P is constant which is true according to ideal gas equation. Hence correct.

In fig 2, T is constant, According to ideal gas equation PV should be constant and P versus V should be a rectangular hyperbola, hence the figure given is wrong.

In figure 3, P and T is directly proportional when V is constant which is true according to ideal gas equation. Hence correct.

In figure 4, PV is not directly proportional to T which is wrong according to ideal gas equation, hence not correct.