MEDIUM
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A thermodynamic system is taken from an original state A to an intermediate state B by a linear process as shown in the figure. Its volume is then reduced to the original value from B to C by an isobaric process. The total work done by the gas from A to B and B to C would be :

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Important Questions on Thermodynamics

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
An ideal gas is compressed to half of its initial volume by means of several processes. Which of the process results in the maximum work done on the gas?
MEDIUM

One mole of diatomic ideal gas undergoes a cyclic process ABC as shown in figure. The process BC is adiabatic. The temperatures at A, B and C are 400 K, 800 K and 600 K respectively. Choose the correct statement :

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EASY
Cp-Cv=RM and Cv are specific heats at constant pressure and constant volume respectively. It is observed that, Cp-Cv=a for hydrogen gas and Cp-Cv=b for nitrogen gas. The correct relation between a and b is:
EASY
2 kg of a monoatomic gas is at a pressure of 4×104 N m-2. The density of the gas is 8kg m-3. What is the order of energy of the gas due to its thermal motion?
HARD
The heat capacity of one mole an ideal is found to be CV=3R1+aRT2 where a is constant. The equation obeyed by this gas during a reversible adiabatic expansion is:
EASY
4.0g of a gas occupies 22.4 liters at NTP. The specific heat capacity of the gas at constant volume is 5.0 J K-1 mol-1 . If the speed of sound in this gas at NTP is 952 m s-1 , then the heat capacity at constant pressure is

(Take gas constant R=8.3 J K-1 mol-1 )
MEDIUM
N moles of diatomic gas in a cylinder is at a temperature T. Heat is supplied to the cylinder such that the temperature remains constant but n moles of the diatomic gas get converted into monoatomic gas. The change in the total kinetic energy of the gas is
MEDIUM
An ideal monoatomic gas occupies a volume of 2 m3 at a pressure of 3×106 Pa. The energy of the gas is:
MEDIUM
For a diatomic ideal gas in a closed system, which of the following plots does not correctly describe the relation between various thermodynamic quantities?
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
EASY
A gas is compressed isothermally to half its initial volume. The same gas is compressed separately through an adiabatic process until its volume is again reduced to half. Then:
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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MEDIUM

An ideal gas is taken reversibly around the cycle a-b-c-d-a as shown on the T (temperature) - S (entropy) diagram

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The most appropriate representation of above cycle on a U (internal energy)-V (volume) diagram is

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

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
MEDIUM
The bulk modulus of a gas is defined as, B=-VdPdV . For an adiabatic process, the variation of B is proportional to Pn. For an ideal gas, n is
EASY

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

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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)
HARD
Consider a spherical shell of radius R at temperature T. The black body radiation inside it can be considered as an ideal gas of photons with internal energy per unit volume u=UVT4 and pressure p=13UV . If the shell now undergoes an adiabatic expansion the relation between T and R is: