Adiabatic Expansion

[kshalbi]

If a gas expands adiabatically and you have to find the work it does, do you use the equation for reversible or irreversible reactions?

[Chem_Mod]

No, you would not use the isothermal equations. The work done would be equal to the internal energy change since U=q+w but q=0 for adiabatic. So all you need to know is the initial and final temperatures to find deltaU then that is also w.

[kshalbi]

Yeah but then to find w do you use: -PdeltaV or the -nRTln (v1/v2). These two equations are what I meant by the "reversible or irreversible" equations for work.

[kshalbi]

Yeah but then to find w do you use: -PdeltaV or the -nRTln (v1/v2). These two equations are what I meant by the "reversible or irreversible" equations for work.

[Alan Chien 1J]

I think what the chem mod is saying is that delta u = q + w. But in an adiabatic expansion q is 0. Therefore U = W. By using a separate equation for U ( change U = 3/2 nRchangeT), you can indirectly solve for W.