Q.

One mole of an ideal diatomic gas expands from volume V to 2V isothermally at a temperature 27°C and does W joule of work. If the gas undergoes same magnitude of expansion adiabatically from 27°C doing the same amount of work W, then its final temperature will be (close to) ______ °C.

(log2=0.693)   [2026]

1 −189  
2 −117  
3 −30  
4 −56  

Ans.

(4)

For isothermal process

Wisothermal=nRTln(V2V1)

     =1·R·300·ln(2)

      =300R(0.693)    (1)

Now for adiabatic process,

It is given work done in isothermal = work done in adiabatic

Wadiabatic=nR(T1-T2)γ-1    (2)

(1)=(2)

nR(300-Tfinal)1.4-1=300R(0.693)

Tfinal=216.84 K

=-56.3°C