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Mechanical Properties Of Fluids

Question
CBSEENPH11020644

4.0 g of a gas occupies 22.4 L at NTP. The specific heat capacity of the gas at constant volume is 5.0 JK-1 mol-1. If the speed of sound in this gas at NTP is 952 ms-1, then the heat capacity at constant pressure is.
(Take gas constant R = 8.3 Jk-1 mol-1)

  • 8.0 JK-1mol-1

  • 7.5 JK-1mol-1

  • 7.0 JK-1mol-1

  • 8.5 JK-1mol-1

Solution

A.

8.0 JK-1mol-1

Given, M = 4 gm
V= 22.4 L, 
CV = 5 JK-1 mol-1
straight v subscript sound space equals 952 space straight m divided by straight s comma
straight C subscript straight p space equals ?
As comma space velocity space of space sound comma space straight v subscript sound space equals space square root of γpV over straight M end root
rightwards double arrow space straight gamma space equals space straight M over pV straight V subscript sound superscript 2 space equals space straight C subscript straight p over straight C subscript straight v
so comma space heat space capacity space at space constant space pressure comma

straight C subscript straight p space equals space straight C subscript straight v open square brackets straight M over pV close square brackets straight v subscript sound superscript 2 space equals space 5 space open square brackets fraction numerator 4 space straight x space 10 to the power of negative 3 end exponent over denominator 10 to the power of 5 space straight x space 22.4 space straight x space 10 to the power of negative 3 end exponent end fraction close square brackets left parenthesis 952 right parenthesis squared

equals fraction numerator 20 over denominator 22.4 end fraction space straight x space left parenthesis 952 right parenthesis squared space straight x space 10 to the power of negative 5 end exponent

equals space 809.200 space straight x space 10 to the power of negative 5 end exponent space equals space 8.09 space straight j divided by mol space straight K.