4.0 g of helium occupies 22400 cm3 at STP. The specific heat capacity of helium at constant pressure is 5.0 cal K–1 mol–1. Calculate the speed of sound in helium at STP.

Given:


4.0 g of helium occupies 22400 cm3 at STP.


The specific heat capacity of helium at constant pressure is 5.0 cal K–1 mol–1 = 21J K–1 mol–1



⇒


⇒


At STP the pressure P is 1.013×105Pa.


The velocity of sound will be where P is the pressure of the gas, V is the volume and M is the mass of the gas.


Thus putting the values given, we get,



The speed of sound in helium is m/s.


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