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NCERT Solutions for class 11 Physics | Chapter 12 - Thermodynamics

Questions
1 Which of the following process is used to do maximum work done on the ideal gas if the gas is compressed to half of its initial volume?
A Isothermal
B Isochoric
C Isobaric
D Adiabatic

Answer:Adiabatic
2 Thermodynamics

Let Q1, Q2 , Q2 heat given to the system in processes A, B, C respectively consider two statements

A. Q1 > Q2 > Q3

B. WA > WB > WC

A Both A & B are Correct
B Both A & B are wrong
C A is Correct Only
D B is Correct Only.

Answer:Both A & B are Correct
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3 What is the molar specific heat of a isothermal & adiabatic process respectively
A ∞ , 0
B 0, ∞
C 0, 0
D none of these

Answer:∞ , 0
4 A vessel contains 4 mole of O2(relative molar mass 32) at temperature T. The pressure is P. An identical vessel contains 1 mole of nitrogen of temperature 2T. find the pressure the
A P/2
B 2P
C 8P
D P

Answer:P/2
5 During an adiabatic process the square of the pressure of a gas is proportional to the fifth power of its absolute temperature. The ratio of specific heat Cp / Cv for that gas is
A 3/5
B 4/3
C 5/3
D 3/2

Answer:5/3
6 An ideal gas who ratio of specific heat Cp / Cv = γ is Expanded according to the law P = av2 when a is constant. The ratio of final volume to Initial value is n .find the ΔU.Initial volume is V0
A aV03 (n3-1) / γ-1
B aV02 (n2 - 1) / γ-1
C aV03 (n3 + 1) /γ+1
D aV02 (n2 + 1) /γ-1

Answer:aV03 (n3-1) / γ-1
7 An ideal gas is taken through a cyclic thermodynamics process through four steps.
The amount of heat involved in the steps are Q1 = 5960 J,Q2 = - 5600 J,Q3= -3000 J,Q4 = -3600 J
respectively. The corresponding quantities of Internal energy changes are ΔU1 = 3.760 J ,ΔU2 = - 4800 J,ΔU3 = -1800 J,ΔU4 = ?

find the value ΔU4 & net work done

A 2930 J, 960 J
B 2830 J, 900 J
C 2930 J, -960 J
D -2930 J, 960 J

Answer:2930 J, 960 J
8 Consider the following statements

(Assertion) The internal energy of an ideal gas does not change during an Isothermal process

(Reason) The decrease in the volume of the gas is compensated by a corresponding increase in pressure when its temperature is constant in accordance with Boyle law

A Both A & R are true and R is correct Explanation of A
B Both A & R are true and R is not correct Explanation of A
C A is true R is false
D A is false but R is true

Answer:Both A & R are true and R is correct Explanation of A.
9 It is known that curves A, B, C are Isobaric, Isothermal, Adiabatic process then when one is correct

Thermodynamics

A A - Adiabatic, B - Isothermal,, C - Isobaric
B A- Isothermal,, B - Adiabatic, C - Isobaric
C A - Isobaric, B - Isothermal C - Adiabatic
D None of these

Answer:A - Adiabatic, B - Isothermal,, C - Isobaric
10 Consider a heat engine as shown in Fig. below Q1 and Q2 are heat added to heat bath T1 and heat taken from T2 in one cycle of engine. W is the mechanical work done on the engine.

If W > 0, then possibilities are:

A Q1 > Q2 > 0
B Q2 > Q1 > 0
C Q2 < Q1 < 0
D Q1 < 0, Q2 > 0

Answer:A, C
11 Consider a cycle followed by an engine (Fig. in below)

1 to 2 is isothermal

2 to 3 is adiabatic

3 to 1 is adiabatic

Thermodynamics

Such a process does not exist because

A heat is completely converted to mechanical energy in such a process, which is not possible.
B mechanical energy is completely converted to heat in this process,which is not possible.
C curves representing two adiabatic processes don’t intersect.
D curves representing an adiabatic process and an isothermal process don’t intersect.

Answer:A, C
12 An ideal gas undergoes isothermal process from some initial state i to final state f. Choose the correct alternatives.
A dU = 0
B dQ= 0
C dQ = dU
D dQ = dW

Answer:A, D
13 Which of the processes described below are irreversible?
A The increase in temperature of an iron rod by hammering it.
B A gas in a small container at a temperature T1 is brought in contact with a big reservoir at a higher temperature T2 which increases the temperature of the gas.
C A quasi-static isothermal expansion of an ideal gas in cylinder fitted with a frictionless piston.
D An ideal gas is enclosed in a piston cylinder arrangement with adiabatic walls. A weight W is added to the piston, resulting in compression of gas.

Answer:A, B, C
14 If an average person jogs, hse 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 0.25 kg
B 2.25 kg
C 0.05 kg
D 0.20 kg

Answer:0.25 kg
15 An ideal gas undergoes four different processes from the same initial state (Fig. in below). Four processes are adiabatic, isothermal, isobaric and isochoric. Out of 1, 2, 3 and 4 which one is adiabatic.

Thermodynamics

A 4
B 3
C 2
D 1

Answer:2
16 Which of the following is the largest unit of energy
A Electron volt
B Joule
C Calorie
D Erg

Answer:Calorie
17 For all the reactions what is the nature of the chemical dissociation?
A Exothermic
B Reversible
C Endothermic
D Reversible and endothermic

Answer:Reversible and endothermic
18 Select the factor that affects the heat of reaction which is based on Kirchoff’s equation
A Molecularity
B Temperature
C Pressure
D Volume

Answer:Temperature
19 A gas is compressed to half of its initial volume isothermally. The same gas is compressed again until the volume reduces to half through an adiabatic process. Then
A Work done during isothermal compression is more
B Work done is independent of the processes used for compression
C Work done is more during the adiabatic process
D Work done is dependent on the atomicity of the gas

Answer:Work done is more during the adiabatic process
20 What is a necessary condition for a reaction to be spontaneous at all temperatures?
A ΔH < ΔG
B ΔG and ΔH should be positive
C ΔH = ΔG = 0
D ΔG and ΔH should be negative

Answer:ΔG and ΔH should be negative

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