Recent content by Lairix

Homework Statement The problem is in the attached .PNG file. Homework Equations none The Attempt at a Solution I believe I am supposed to do a Legendre transform but have no idea where to begin...

I understand what you are saying. However, I am still confused as to what you are considering the system to be: the vessel or the gas? If the system is the gas, then it makes sense that Q has a value(not zero) and that W = 0(but only if it is expanding against a vacuum). However, if the system...

Homework Statement 10 moles of an ideal gas Cv = 20.8 J/mol at T0 = 300 K and P0 =0.3 MPa occupy the left half of an insulated vessel. At time t=0 a 1 kW electrical heating element is turned on. after 30 s, the partition dividing the vessel ruptures and the heating element is turned off...

I don't understand how Delta(U) = Cvdelta(T) is always true for Ideal Gases...Shouldn't this only be true for constant volume processes? Yet it seems to be used even when a gas is expanding or being compressed... Any ideas...Thanks in advance.

I don't understand how we can tell if this a reversible or irreversible process to begin with. Moreover, why are we using time in the force-balance equation. I was under the impression that thermodynamics does not attempt to make claims about what is happening over time, but only what is...

Oh, no...How silly of me! :) Good catch, AM! Revised: Fgravity= 1,470 N Fgravity + Patm*0.12m 2 = PHe gas*0.12 m2

Thanks Chet and AM for all your help. Chet, I have written the force balance for the piston below: The forces on the piston are the mass (since it fell due to gravity) and the force of the atmosphere (air molecues above the piston). These forces should be balanced by the pressure of helium...

Ok. I considered using Cv earlier, But then I realized that this is neither a constant pressure or constant voume process, because Helium gas is being compressed. ...Would I use the ideal gas law, PV= nRT to solve for the initial volume and then Cp= Cv +R to find Cp? After that, I could use...

This adiabatic compression, I believe, so delta U= W... Work is the integral of PdV or Fdx... However, in this case, we know neither the change in volume or displacement. Also, I'm confused on how to incorporate the atmospheric pressure in this.

Homework Statement An insulated vertical cylindrical vessel of cross-sectional area A= .12m^2 contains 20 mol of He gas at To= 300K and Po= .5 bar. It is capped by a movable piston of mass m = 150kg supported from the ceiling by a wire. The top of the vessel is open to the atmosphere (Patm =...