CBSE Class 11 Thermodynamics Worksheet D

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Question. During an isothermal expansion, a confined ideal gas does –150 J of work against its surroundings. This implies that
(a) 150 J heat has been removed from the gas
(b) 300 J of heat has been added to the gas
(c) no heat is transferred because the process is isothermal
(d) 150 J of heat has been added to the gas

Answer: A,D

Question. When 1 kg of ice at 0°C melts to water at 0°C, the resulting change in its entropy, taking latent heat of ice to be 80 cal/°C, is
(a) 273 cal/K
(b) 8 × 104 cal/K
(c) 80 cal/K
(d) 293 cal/K

Answer: D

Question. During an adiabatic process, the pressure of a gas is found to be proportional to the cube of its temperature. The ratio of ^Cp/^Cv for the gas is
(a) 2
(b) 5/3
(c) 3/2
(d) 4/3

Answer: C

Question. A system is taken from state a to state c by two paths adc and abc as shown in the figure. The internal energy at a is Ua = 10 J. Along the path adc the amount of heat absorbed δQ₁ = 50 J and the work done δW₁ = 20 J whereas along the path abc the heat absorbed δQ₂ = 36 J. The amount of work done along the path abc is
(a) 6 J
(b) 10 J
(c) 12 J
(d) 36 J

Answer: A

Question. 1 gm of water at a pressure of 1.01 × 10⁵ Pa is converted into steam without any change of temperature. The volume of 1 g of steam is 1671 cc and the latent heat of evaporation is 540 cal. The change in internal energy due to evaporation of 1 gm of water is
(a) ≈ 167 cal
(b) ≈ 500 cal
(c) 540 cal
(d) 581 cal

Answer: B

Question. The internal energy change in a system that has absorbed 2 kcals of heat and done 500 J of work is
(a) 6400 J
(b) 5400 J
(c) 7900 J
(d) 8900 J

Answer: C

Question. Three copper blocks of masses M₁, M₂ and M₃ kg respectively are brought into thermal contact till they reach equilibrium. Before contact, they were at T₁, T₂, T₃ (T₁ > T₂ > T₃). Assuming there is no heat loss to the surroundings, the equilibrium temperature T is (s is specific heat of copper) 

Answer: B

Question. A thermodynamic system undergoes cyclic process ABCDA as shown in fig. The work done by the system in the cycle is : 

(a) P₀V₀
(b) 2P₀V₀
(c) P₀V₀/2
(d) Zero

Answer: D

Question. A monoatomic gas at a pressure P, having a volume V expands isothermally to a volume 2V and then adiabatically to a volume 16V. The final pressure of the gas is :(take γ =5/3)
(a) 64P
(b) 32P
(c) P/64
(d) 16P

Answer: C

Question. Figure below shows two paths that may be taken by a gas to go from a state A to a state C. (14 EX 3)
In process AB, 400 J of heat is added to the system and in process BC, 100 J of heat is added to the system. The heat absorbed by the system in the process AC will be 
(a) 500 J
(b) 460 J
(c) 300 J
(d) 380 J

Answer: B

Question. A carnot engine having an efficiency of 1/10 as heat engine, is used as a refrigerator. If the work done on the system is 10 J, the amount of energy absorbed from the reservoir at lower temperature is :-
(a) 90 J
(b) 99 J
(c) 100 J
(d) 1 J

Answer: A

Question. For an isothermal expansion of a perfect gas, the value of ΔP/P is equal to 

Answer: B

Question. If an average person jogs, he produces 14.5 × 103 cal/min. This is removed by the evaporation of sweat. The amount of sweat evaporated per minute (assuming 1 kg requires 580 × 10³ cal for evaporation) is
(a) 0.025 kg
(b) 2.25 kg
(c) 0.05 kg
(d) 0.20 kg

Answer: A

Question. Consider p-V diagram for an ideal gas shown in figure. 

Out of the following diagrams, which figure represents the T-p diagram?
(a) (iv)
(b) (ii)
(c) (iii)
(d) (i)

Answer: C

Question. A gas is taken through the cycle A→ B→ C→ A, as shown in figure. What is the net work done by the gas ?
(a) 1000 J
(b) zero
(c) – 2000 J
(d) 2000 J

Answer: A

Question. An ideal gas goes from state A to state B via three different processes as indicated in the P-V diagram : (43)
If Q₁, Q₂, Q₃ indicate the heat a absorbed by the gas along the three processes and ΔU₁, ΔU₂, ΔU₃ indicate the change in internal energy along the three processes respectively, then
(a) Q₁ > Q₂ > Q₃ and ΔU₁ = ΔU₂ = ΔU₃
(b) Q₃ > Q₂ > Q₁ and ΔU₁= ΔU₂ = ΔU₃
(c) Q₁ = Q₂ = Q₃ and ΔU₁ > ΔU₂ > ΔU₃
(d) Q₃ > Q₂ > Q₁ and ΔU₁> ΔU₂ > ΔU3

Answer: A

Question. Thermodynamic processes are indicated in the following diagram : 

Match the following
Column-1 Column-2
P. Process I A. Adiabatic
Q. Process II B. Isobaric
R. Process III C. Isochoric
S. Process IV D. Isothermal
(a) P → C, Q → A, R → D, S → B
(b) P → C, Q → D, R → B, S → A
(c) P → D, Q → B, R → A, S → C
(d) P → A, Q → C, R → D, S → B

Answer: A

Question. A diatomic gas initally at 18ºC is compressed adiabatically to one eighth of its original volume. The temperature after compression will be
(a) 18ºC
(b) 887ºC
(c) 327ºC
(d) None of these

Answer: D

Question. The figure shows the P-V plot of an ideal gas taken through a cycle ABCDA. The part ABC is a semi-circle and CDA is half of an ellipse. Then,
(a) the process during the path A → B is isothermal
(b) heat flows out of the gas during the path B → C → D
(c) work done during the path A → B → C is zero
(d) positive work is done by the gas in the cycle ABCDA

Answer: D

1. If a air is a cylinder is suddenly compressed by a piston. What happens to the pressure of air?

2. What is the ratio of find volume to initial volume if the gas is compressed adiabatically till its temperature is doubled?

3. What is the ratio of slopes of P-V graphs of adiabatic and isothermal process?

4. A motor car tyre has a Pressure of four atmosphere at a room temperature of 27°C. If the tyre suddenly bursts, calculate the temperature of escaping gas?

5. How does Carnot cycle operates?

6. Calculate the work done by the gas in going from the P-V graph of the thermodynamic behavior of a gas from point A to point B to point C?

7. Why does absolute zero not correspond to zero energy?

8. State the Second law of thermodynamics and write 2 applications of it?

9. At 0°C and normal atmospheric pressure, the volume of 1g of water increases from 1cm³ to 1.091 cm³ on free zing. What will be the change in its internal energy? Normal atmospheric pressure is 1.013x10⁵ N|m2 and the latent heat of melting of ice is 80 cal/g? 

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