Q.

An ideal gas is expanding such that PT2=constant. The coefficient of volume expansion of the gas is                 [2008]

1 1T  
2 2T  
3 3T  
4 4T  

Ans.

(3)

pT2=constant  (given)

∴ (nRTV)T2=constant   or    T3V-1=constant

(∴ PV=nRT)

Differentiating the equation, we get

3T2VdT-T3V2dV=0   or   3dT=TVdV         ⋯(i)

From the equation

dV=Vγ dT

γ=coefficient of volume expansion of gas=dVV·dT

From eq. (i)   γ=dVV·dT=3T