ENTROPY

Question 1. When the entropy of a system is increasing:

(a) the system is moving towards equilibrium
(b) the system is moving away from equilibrium
(c) the available energy is increasing
(d) the available energy is decreasing.

Question 2. Spontaneous changes involve:

(a) an increase in entropy
(b) a decrease in entropy
(c) no change in entropy
(d) quasistatic process.

Question 3. The change in entropy of a gas when moving from state 1 to state 2 is:

(a) dependent on the path taken by the process between 1 and 2
(b) independent of the path taken by the process between 1 and 2
(c) dependent on the other state properties of the substance
(d) independent of the other state properties of the substance.

Question 4. During a cycle consisting of irreversible processes:

(a) the entropy of the environment may increase or decrease
(b) the entropy of the environment decreases
(c) the entropy of the environment increases
(d) the entropy of the environment remains unchanged.

Question 5. During a cycle consisting of reversible processes the ratio Q_H/T_H:

(a) is greater than Q_L/T_L

(b) is less than Q_L/T_L

(c) is equal to Q_L/T_L

(d) can be greater or less than Q_L/T_L

Question 6. A Carnot engine

(a) neither increases nor decreases the entropy of the environment
(b) increases the entropy of the environment
(c) decreases the entropy of the environment
(d) may increase or decrease the entropy of the environment.

Question 7. Which of the following will increase the efficiency of a heat engine?

(a) Make T_H and T_L equal
(b) Increase T_H
(c) Increase T_L
(d) Decrease T_L.

Question 8. An ideal gas undergoes an isobaric process when the temperature increases. Does the entropy of the gas:
(a) increase
(b) decrease
(c) stay the same
(d) not enough information.

Question 9. An ideal gas undergoes an isochoric process where the pressure increases. Does the entropy of the gas:
(a) decrease
(b) stay the same
(c) increase
(d) not enough information.

Question 10. (a) 5 kg of gas occupying a volume of 6 m³ at a temperature of 200°C receives heat at constant pressure until its temperature becomes 500°C. Calculate the change in entropy.

For the gas, take c_p = 1.006 kJ kg^-1 K^-1 and c_v = 0.717 kJ kg^-1 K^-1.

(b) If after reaching 500°C the gas then rejects heat at constant volume until its pressure is reduced to 50 kN m^-2, calculate the change of entropy.