Mark the correct statement regarding entropy.

1.	At 0°C, the entropy of a perfectly crystalline substance is taken to be zero.
2.	At absolute zero temperature, the entropy of a perfectly crystalline substance is positive.
3.	At absolute zero temperature, the entropy of all crystalline substances is taken to be zero.
4.	At absolute zero temperature, the entropy of a perfectly crystalline substance is taken to be zero.

An engine operating between 150°C and 25°C takes 500 J heat from a higher temperature reservoir if there are no frictional losses, then work done by engine is [MH CET 1999]

(1) 147.7 J

(2) 157.75 J

(3) 165.85 J

(4) 169.95 J

The standard entropies of CO₂(g), C(s) and O₂(g) are 213.5, 5.690 and 205 JK^–1 respectively. The standard entropy of formation of CO₂(g) is

(1) 1.86 JK^–1

(2) 1.96 JK^–1

(3) 2.81 JK^–1

(4) 2.86 JK^–1

Equal volumes of monoatomic and diatomic gases at same initial temperature and pressure are mixed. The ratio of specific heats of the mixture (C_p/C_v) will be [AFMC 2002]

(1) 1

(2) 2

(3) 1.67

(4) 1.5

The unit of entropy is -

1. J mol^–1

2. JK mol^–1

3. J mol^–1 K^–1

4. J^–1 K^–1 mol^–1

The entropy changed involved in the conversion of 1 mole of liquid water at 373 K to vapour at the same temperature will be $[\Delta H_{\text{vap}}=2.257kJ/gm]$ [MP PET 2002]

(1) 0.119 kJ

(2) 0.109 kJ

(3) 0.129 kJ

(4) 0.120 kJ

During the boiling of a liquid, which of the following thermodynamic changes take place?

1. An increase in entropy

2. A decrease in entropy

3. An increase in heat of vaporization

4. An increase in free energy

During a thermodynamic process, a gas inside a cylinder is compressed, requiring 462 Joules of work to be done on the system. Throughout this compression, 128 Joules of heat energy is released into the surroundings. What is the net change in the internal energy (\(\Delta U\)) of the gas?

1. +590 J

2. –334 J

3. +334 J

4. –590 J

For a carnot engine, the source is at 500 K and the sink at 300 K. What is efficiency of this engine

(1) 0.2

(2) 0.4

(3) 0.6

(4) 0.3

From Kirchhoff's equation which factor affects the heat of reaction [MP PMT 1990]

1. Pressure

2. Temperature

3. Volume

4. Molecularity