Question

Q6. A system composed of 2 kg of the above fluid expands in a frictionless piston and cylinder 

machine from an initial state of 1 MPa, 100°C to a final temperature of 30°C. If there is no heat 

transfer, find the net-work for the process.

Answer 1

$$pV=\frac{m}{M}RT$$

$$\frac {p_1V_1}{T_1}=\frac {p_2V_2}{T2}$$

$$p_1=1 MPa$$

$$t_1=100^0C$$

$$t_2=30^0C$$

$$p_2 \frac {V_2}{V_1}=\frac {p_1T_1}{T_2}=1.231 MPa$$