Chemical Thermodynamics 3.6 - Adiabatic Processes

Short physical chemistry lecture on reversible adiabatic expansion and compression of ideal gases.

Adiabatic processes are those which occur without any heat. The relationship between final and initial temperature and volume in an adiabatic process depends on the constant volume heat capacity, which varies depending on the type of molecule in an ideal gas.

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[Randomproductions]

Thank you for putting these videos together! I am a chemistry major currently taking thermodynamics, and to be honest I find these videos more useful than my lecture.

[maxpiepgras]

When you first take the integral of Cv(T)/T dT, you accidentally wrote Cv ln(Tf/Vi) instead of Cv ln(Tf/Ti), just letting you know! These videos are great, thank you so much for putting the time in to make these!

[wedfrest]

All these videos of yours are absolutely fantastic 👌

[NickB]

Does DeltaU=W? or does it equal negative work? I can't remember if it's this subject where us chemist have it different than engineers

[nkyu]

1) Equation du=C_v(T)dT is derived from equation Cv(T)=(du/dT)_V which has a restriction of constant volume.
And it seems the former equation doesn't have the same restriction. Or C_v gives the whole terms in the former equation the mentioned restriction?
Or is there an assumption that this equation is true only for a small change of volume?

2) Adiabatic process means no heat and there could be change in volume. then why do we use C_v(T) which seems far from the adiabatic process ?

3) Why did you assume C_V(T)=C_V when C_V=3/2nR?
At first I Thought it is for the final result to be applicable for non-ideal case, but it seems we can't get to the result at all for non-ideal case because dw=-nRT/V *dV.

[souravsarkar]

Why's it a reasonable approximation of it's in tens of Kelvin but not a reasonable one of it's hundreds of Kelvin?

[salymamani]

so work can be calculated like in an isothermal process(nRT ln(V2/V1))? But if so wouldn't that mean that work in isothermal and adiabatic process is the same, but its not.

[nkyu]

I'm not sure how ΔrH is a state function. isn't dependent of path which includes Hf and Hi?

and in the video about "State and Path Functions", there was eqn Δu=w+q. w and q are pathfunctions. does it say Δu is pathfunction?

[andreipaulau]

Why are we allowed to use the heat capacity at constant volume where the volume is clearly not constant?

[Sebochan]

Will the value of n change if an ideal gas went under adiabatic process? Or the n will always be n = 1 mol?

[ameer]

What if volume, pressure and temperature are all changing? Could the heat capacity in the last integral on the left side be changed to the ideal gas law in terms of temperature?