Q.
Find the minimum attainable pressure of an ideal gas in process T=T0+αV2 , where T0 and α are positive constants and V is the volume of one mole of gas.
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NTA AbhyasNTA Abhyas 2020Thermodynamics
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Solution:
Given, T=T0+αV2 ...(i)
For 1 mol of a gas, PV=RT
of V=PRT
Substituting this value in Eq. (i), we get T=T0+α(PRT)2=T0+αP2R2T2
or TP2=T0P2+αR2T2
or P=αRT(T−T0)−1/2 ...(ii)
After differentiating, we get dTdP=αR[(T−T0)−1/2−21T(T−T0)−3/2]
For minimum pressure, dTdP=0 ∴0=αR[(T−(T)0)−1/2−21T(T−(T)0)−3/2]
After solving, T = 2T0
From Eq. (ii), Pmin=αR2T0(2T0−T0)−1/2 =2RαT0