Friday, March 30, 2007
Fri-Day 4
AP: ack! I had a feeling that I gave some misinformation on Thursday. The last problem that we did, the generic Thermo problem, was solved correctly; however, I suggested an alternate way to get delta S of the reaction was to get the individual entropy, S, of each reactant and product via the delta Gf and the delta Hf values. THAT IS NOT POSSIBLE and it goes to the heart of the MAJOR DIFFERENCE between ABSOLUTE entropy, S, and a change in entropy, delta Sf. There is NO such equation as delta Gf = delta Hf - TS (which is what I erroneously suggested to use). There IS only delta Gf = delta Hf - T delta Sf ! The delta Sf values were not given and are not equivalent to the ABSOLUTE entropies of the reactants and products, anyway. If you think about it, for an element, "delta Gf = delta Hf - T delta Sf" is a useless equation because delta Gf and delta Hf are zero for elements in their standard states! Therefore, delta Sf for an element would also be zero even though we know that ABSOLUTE entropy CANNOT be zero for ANY element under any circumstances (except at the ridiculous temperature of zero Kelvin).
Bottom line: solve that type of problem as we did in class and ignore any alternate way (there is none).
Do all of the Thermo worksheets and any additional assigned problems to be posted this weekend.
Here is a link to some college Thermo lectures that you can use for review:
Complete lecture list from Texas A&M General Chem
Entropy Lecture
Free Energy Lecture
Texas A&M Class Website with Notes
Honors: we did another enthalpy diagram, this time for an endothermic reaction. We drew and labeled the nine arrows associated with the regular and catalyzed reaction.
We then discussed and defined equilibrium: phase, solution, and chemical. Juniors, study the relevant notes and do the text reading; come to extra help if you have any questions about this lesson. Look for the vacation assignment to be posted this weekend.
Regents: we completed an enthalpy diagram based on information
from Table I. We labeled each arrow and then did some calculations from the diagram.
We then defined the term "equilibrium".
Those who missed this class, study the relevant notes and do the text reading; come to extra help if you have any questions about this lesson.
Look for the vacation assignment to be posted this weekend.
Bottom line: solve that type of problem as we did in class and ignore any alternate way (there is none).
Do all of the Thermo worksheets and any additional assigned problems to be posted this weekend.
Here is a link to some college Thermo lectures that you can use for review:
Complete lecture list from Texas A&M General Chem
Entropy Lecture
Free Energy Lecture
Texas A&M Class Website with Notes
Honors: we did another enthalpy diagram, this time for an endothermic reaction. We drew and labeled the nine arrows associated with the regular and catalyzed reaction.
We then discussed and defined equilibrium: phase, solution, and chemical. Juniors, study the relevant notes and do the text reading; come to extra help if you have any questions about this lesson. Look for the vacation assignment to be posted this weekend.
Regents: we completed an enthalpy diagram based on information
from Table I. We labeled each arrow and then did some calculations from the diagram.
We then defined the term "equilibrium".
Those who missed this class, study the relevant notes and do the text reading; come to extra help if you have any questions about this lesson.
Look for the vacation assignment to be posted this weekend.
# posted by C @ 10:48 PM 
