Thermodynamics (Physics) · Question 38

When 1 kg of ice at 0 melts to water at 0 , the resulting change in its entropy, taking latent heat of ice to be 80 cal/g, is

1. 273 cal/K
2. 8 104 cal/K
3. 80 cal/K
4. 293 cal/K

If cp and cv denote the specific heats (per unit mass) of an ideal gas of molecular weight M, then

1. cp - cv = RM2
2. cp - cv = R
3. cp - cv = RM
4. cp - cv = MR

A monatomic gas at pressure P1 and volume V1 is compressed adiabatically to 18th of its original volume. What is the final pressure of the gas?

1. 64P1
2. P1
3. 16P1
4. 32P1

If and represent the increase in internal energy and work done by the system respectively in a thermodynamical process, which of the following is true?

1. = - , in an adiabatic process
2. = , in an isothermal process
3. = , in an adiabatic process
4. = - , in an isothermal process

The internal energy change in a system that has absorbed 2 kcal of heat and done 500 J of work is

1. 6400 J
2. 5400 J
3. 7900 J
4. 8900 J

In thermodynamic processes which of the following statements is not true ?

1. In an isochoric process pressure remains constant.
2. In an isothermal process the temperature remains constant.
3. In an adiabatic process PV = constant.
4. In an adiabatic process the system is insulated from the surroundings.

If Q, E and W denote respectively the heat added, change in internal energy and the work done in a closed cyclic process, then

1. E = 0
2. Q = 0
3. W = 0
4. Q = W = 0

An engine has an efficiency of 1/6. When the temperature of sink is reduced by 62 , its efficiency is doubled. Temperatures of the source is

1. 37
2. 62
3. 99
4. 124

A Carnot engine whose sink is at 300 K has an efficiency of 40%. By how much should the temperature of source be increased so as to increase its efficiency by 50% of original efficiency?

1. 380 K
2. 275 K
3. 325 K
4. 250 K

The molar specific heat at constant pressure of an ideal gas is (7/2) R. The ratio of specific heat at constant pressure to that at constant volume is

1. 9/7
2. 7/5
3. 8/7
4. 5/7