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Mechanical Properties Of Fluids

Question
CBSEENPH11020798

The molar specific heat at constant pressure of an ideal gas is (7/2)R. The ratio of specific heat at constant pressure to that at constant volume is

  • 7/5

  • 8/7

  • 5/7

  • 9/7

Solution

A.

7/5

We have given molar specific heat at constant pressure
         straight C subscript straight P space equals space 7 over 2 straight R
Mayor's relation can be written as:
Molar specific heat at constant volume = Gas constant
i.e.,     CP - CV = R
    rightwards double arrow space space space space straight C subscript straight V space equals space straight C subscript straight P space minus space straight R
space space space space space space space space space space space equals space 7 over 2 straight R space minus space straight R space equals space 5 over 2 straight R
Hence, required ratio is
        straight gamma space equals space straight C subscript straight P over straight C subscript straight V space equals fraction numerator left parenthesis 7 divided by 2 right parenthesis straight R over denominator left parenthesis 5 divided by 2 right parenthesis straight R end fraction equals 7 over 5