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Concepts Of Physics MCQ Edition [Volume 2]
Exam
Concepts Of Physics MCQ Edition [Volume 2]
Subject
Physics
Chapter
Specific Heat Capacities of Gases

Concepts Of Physics MCQ Edition [Volume 2] · Physics · Specific Heat Capacities of Gases

An ideal gas undergoes a process where its pressure and volume vary...

An ideal gas undergoes a process where its pressure and volume vary according to the relation p=kVp = kV. The molar heat capacity of the gas for this process is given by

Options

  1. ACV+R2C_V + \dfrac{R}{2}
  2. BCV+RC_V + R
  3. CCV−RC_V - R
  4. DCV−R2C_V - \dfrac{R}{2}

Correct answer

A. CV+R2C_V + \dfrac{R}{2}

Step-by-step solution

The equation of the process is given by p=kVp = kV, which can be written as pV−1=constantpV^{-1} = \text{constant}.

This represents a polytropic process of the form pVn=constantpV^n = \text{constant}, where n=−1n = -1.

The molar heat capacity for a polytropic process is given by C=CV+R1−nC = C_V + \dfrac{R}{1-n}.

Substituting n=−1n = -1, we get:

C=CV+R1−(−1)C = C_V + \dfrac{R}{1 - (-1)}

C=CV+R2C = C_V + \dfrac{R}{2}

Alternatively, using the ideal gas law pV=RTpV = RT (for one mole)andp=kVand p = kV, we get kV2=RTkV^2 = RT.

Differentiating both sides, 2kVdV=RdT2kV dV = R dT, which gives 2pdV=RdT2p dV = R dT, so pdV=RdT2p dV = \dfrac{R dT}{2}.

From the first law of thermodynamics, dQ=dU+dWdQ = dU + dW.

CdT=CVdT+pdVC dT = C_V dT + p dV

CdT=CVdT+RdT2C dT = C_V dT + \dfrac{R dT}{2}

C=CV+R2C = C_V + \dfrac{R}{2}
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