Wednesday, May 18, 2011

Isothermal Reversible Expansion Work of an IDEAL Gas

Consider an ideal gas confined in a cylinder with a frictionless piston. The reversible
expansion of gas takes place in a finite number of infinitesimally small
intermediate steps. If the Pext is infinitesimally less than internal
pressure of gas ‘P’ by ‘dP’. Then gas expands reversibly and piston moves
through a distance ‘dl’.              
Since dP is so small, for all practical purposes.                              
Pext.  – Pgas  = P.              
One work done by gas in one infinitesimal step (dw) can be expressed as;                              
dw   =   P  ´  dV.         [ w = P ´ DV]                        
\dw  =   PdV.                            
If the gas expands from V1 to V2 during isothermal
reversible expansion. The total amount of work done would be equal to


  1. This comment has been removed by the author.

  2. What if no of moles remains same

  3. what will be the enthalpy change

  4. what will be the enthalpy change