Question

A mass of an ideal gas of volume V at pressure P undergoes the cycle of changes shown in the graph –

At which point is the gas coolest and hottest ?

Coolest hottest

• A. X Y
• B. Y X
• C. Y Z
• D. Z Y

Answer 1

Answer: (C)

Y Z

Answer 2

For a mole of an ideal gas, the equation of state is PV = RT

or T = $\frac{PV}{R}$

which is proportional to the product pV

At x , PV = (4 × 10⁵) (1 × 10^–4) = 40 Nm

At y, pV = (1 × 10⁵) (5 × 10^–4) = 50 Nm

At z, pV = (1 × 10⁵) (1 × 10^–4) = 10 Nm

Thus, T is maximum at y since pV is the highest and T is minimum at z since pV is the smallest

PV = RT