Fundamental Equation (Helmholtz Energy)

[@MatheusBalenMe]

Great video, keep up the good work.

[@PhysicalChemistry]

Thanks for the comment, I really appreciate it

[@ingridcabrera17]

Thanks Professor Stuart, for your outstanding videos! Profesor: What is the Physical meaning (what kind of energy) does the term SdT stands for? If I place S on the Y axis and T on the X axis, what would the area under the curve mean? And why does a delta T cancels out with a nomimal T on this term?

[@melevarck]

Thank you for your amazing lectures! I have one question: why can we take the derivative of A with respect to either T or V when the formulation of the Helmholtz free energy assumes both as constants? Shouldn't these partial derivatives be zero by definition?

[@PhysicalChemistry]

Good question; this is a really common misconception. The **definition** of the Helmholtz energy (A = U - TS) doesn't assume anything about constant T or V. So it is fine to talk about ∂A/∂T or ∂A/∂V, and these are not necessarily zero. The Helmholtz energy is most useful, though, when T and V are constant, and these are the conditions where it is typically used. And, indeed, under those conditions dA = 0 for an equilibrium system.

[@melevarck]

@@PhysicalChemistry I see, thank you very much!

[@skydivenext]

I knew it I fricking knew it my teacher teached bad but didnt now this bad he put in his written book and explanation thatdA=---PdV-SdT when it should be dA=+++++PdV-SdT idk why he wrote he even deducted from dU=dq-dWr which is wrong too,i dont even know why because he used dU=dqr+dWr when using for gibbs so idk why he did different with helmholtz , so is not because he didnt use standar because he did but suddenly changed idk why