Lec 15 | MIT 5.60 Thermodynamics & Kinetics, Spring 2008

[eryaman4]

I don't understand (around the 40 minute mark) how he was able to generalize the value of epsilon to any value (ie., J/mol), when during the derivation the assumption of an infinitesimally small epsilon allowed him to keep the chemical potential of each species constant.

Could someone explain?

[PointOnACurve]

Epsilon is assumed to be a positive scaler, because we'er letting it proceed a little bit forward. Then, the sign of delta G only depend on what in brakets. So, you can ignore epsilon. We would have used dni, but the coefficients are different, So, we use a small "amount of reaction", epsilon. Note, that dni goes to epsilon as either goes to zero.

[eryaman4]

@PointOnACurve Well, what I was wondering was how earlier in the derivation (around 32 minutes), he had chemical potential be a constant rather than a function because the reaction was only preceding an infinitesimally small amount.

But I think I understand now; the deltaG is just written in different units as /mol, but both the epsilon and /mol are referring to the "instantaneous" deltaG. For some reason I didn't realize that deltaG is only one value at a certain point in the reaction.

[almuzcallo]

Kx=Kp*P^(-Δn)

[almuzcallo]

la Kp. queda en funcion de P a la delta niu. No a la menos delta niu

[ahiJabo]

wow! very goood class!

I have an exam next friday about that.....