Q.

A monatomic gas at a pressure P, having a volume V expands isothermally to a volume 2V and then adiabatically to a volume 16V. The final pressure of the gas is (Take γ=53)         [2014]
 

1 64 P  
2 32 P  
3 P/64  
4 16 P  

Ans.

(3)

First, isothermal expansion

PV=P'(2V)P'=P2

Then, adiabatic expansion, P'(2V)γ=Pf(16V)γ

(For adiabatic process, PVγ = constant)

         P2(2V)5/3=Pf(16V)5/3

Pf=P2(2V16V)5/3=P2(18)5/3=P2(123)5/3=P64