Discussion Forum



1)

An ideal gas is expanded form (p1, V1, T1) to ( p2, V2, T2) under different conditions. The correct statement(s) among the following is (are)


A) The work done by the gas is less when it is expanded reversibly from $V_{1}$ to $V_{2}$  under adiabatic conditions as compared to that when expanded reversibly from  $V_{1}$ to $V_{2}$ under isothermal conditions

B) The change in internal energy of the gas is (i) zero, if it is expanded reversibly with $T_{1}$=$T_{2}$ . and (ii) positive,  if it is expanded reversibly under adiabatic conditions with $T_{1}$ $\neq$ $T_{2}$

C) If the expansion carried out freely, it is simultaneous both isothermal as well as adiabatic.

D) The work done on the gas is maximum when it is compressed irreversibly from ($P_{2},V_{2}$) to ($P_{1},V_{1}$ ) against constant pressure $P_{1}$

Answer:

Option A,C,D

Explanation:

112202082_irrevesib.PNG

Irreversible Compression

1122020573_reversible.JPG

Reversible compression

Maximum work is done on the system when compression occurs irreversible and minimum work is done is reversible compression

(b)

    1122020529_isother.JPG

AB is isothermal and AC  is the adiabatic path. Work was done in an area under the curve. Hence, less work is obtained in adiabatic process than in isothermal process.

  (c)   It is incorrect. In adiabatic expansion cooling is observed , hence 

  $\triangle U=nC_{v}\triangle T<0$

(d)   q=0( adibatic) W=0(Free expansion)

Hence   Δ U=0 , Δ T=0( isothermal)