EASY
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During isobaric compression, the volume is held constant and work done by the system will zero then only change occur that a gas internal energy.

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Important Questions on Thermodynamics

HARD
An ideal gas is undergoing a cyclic thermodynamic process in different ways as shown in the corresponding P-V diagrams in column 3 of the table. Consider only the path from state 1 to state 2. W denotes the corresponding work done on the system. The equations and plots in the table have standard notations as used in thermodynamic process. Here γ is the ratio of heat capacities at constant pressure and constant volume. The number of moles in the gas is n.
Column – 1 Column – 2 Column – 3
(I) W12=1γ-1P2V2-P1V1 (i) Isothermal (P) Question Image
(II) W12= -PV2+PV1 (ii) Isochoric (Q) Question Image
(III) W12=0 (iii) Isobaric (R) Question Image
(IV) W12= -nRTlnV2V1 (iv) Adiabatic (S) Question Image
Which one of the following options correctly represents a thermodynamic process that is used as a correction in the determination of the speed of sound in ideal gas?
MEDIUM

In the P-V diagram below the dashed curved line is an adiabatic

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For a process that is described by a straight line joining two points X and Y on the adiabatic (solid line in the diagram), heat is: (Hint: Consider the variations in temperature from X and Y along the straight line)

MEDIUM
A monoatomic gas is compressed from a volume of 2 m3 to a volume of 1 m3 at a constant pressure of 100 N m2. Then it is heated at constant volume by supplying 150 J of energy. As a result, the internal energy of the gas
EASY

For the given cyclic process CAB as shown for a gas, the work done is:

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EASY
For a rigid diatomic molecule, the universal gas constant R=nCP, where, CP is the molar specific heat at constant pressure and n is a number. Hence, n is equal to
HARD
A mixture of ideal gas containing 5 moles of monatomic gas and 1 mole of rigid diatomic gas is initially at pressure P0, volume V0 and temperature T0. If the gas mixture is adiabatically compressed to a volume V04, then the correct statement(s) is/are,
(Given 21.2= 2.3; 23.2=9.2; R is gas constant)
MEDIUM

The three processes in a thermodynamic cycle shown in the figure are : Process 12 is isothermal; Process 23 is isochoric (volume remains constant); Process 13 is adiabatic.

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The total work done by the ideal gas in this cycle is,10 J. The internal energy decreases by, 20 J in the isochoric process. The work done by the gas in the adiabatic process is, -20 J. The heat added to the system in the isothermal process is

HARD
Consider a mixture of n moles of helium gas and 2n moles of oxygen gas (molecules taken to be rigid) as an ideal gas. Its CPCV value will be:
HARD
 An engine operates by taking n moles of an ideal gas through the cycle ABCDA shown in figure. The thermal efficiency of the engine is:

(Take Cv=1.5R, whereR is gas constant)

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EASY
An ideal gas has molecules with 5 degrees of freedom. The ratio of specific heats at constant pressure Cp and at constant volume CV is:
EASY
A diatomic gas with rigid molecules does 10 J of work when expanded at constant pressure. What would be the heat energy absorbed by the gas, in this process?
EASY
Half mole of an ideal monoatomic gas is heated at a constant pressure of 1atm from 20° C to 90° C. Work done by the gas is(Gas constant,R=8.21 J mol-1 K-1)
EASY

The given diagram shows four processes i.e., isochoric, isobaric, isothermal and adiabatic. The correct assignment of the processes, in the same order is given by:
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MEDIUM
Starting at temperature 300K, one mole of an ideal diatomic gas γ=1.4 is first compressed adiabatically from volume V1 to V2=V116. It is then allowed to expand isobarically to volume 2V2 . If all the processes are the quasi-static then the final temperature of the gas (in K) is (to the nearest integer) ___________.
EASY
A thermodynamics system undergoes cyclic process ABCDA as shown in Figure. The work done by the system in the cycle is:
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MEDIUM
Consider two ideal diatomic gases A and B at some temperature T . Molecules of the gas A are rigid, and have a mass m . Molecules of the gas B have an additional vibrational mode and have a mass m4 . The ratio of the specific heats CV Aand  CVB of gas A and B, respectively is:
MEDIUM
Two moles of an ideal gas, with CPCV=53, are mixed with three moles of another ideal gas CPCV=43. The value of CPCV for the mixture is
EASY

Thermodynamic processes are indicated in the following diagram.

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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
EASY

One mole of an ideal diatomic gas undergoes a transition from A to B along a path AB as shown in the figure,

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The change in internal energy of the gas during the transition is:

EASY
n moles of an ideal gas with constant volume heat capacity Cv undergo an isobaric expansion by certain volume. The ratio of the work done in the process, to the heat supplied is: