Wednesday, March 28, 2007
Wednes-Day 2
Honors: we did more thermochemical equations and related those reactions or processes to enthalpy diagrams. We varied the mole quantities and calculated a proportional change in the quantity of heat absorbed or released.
We then discussed two of the five factors that can AFFECT the rate (number of EFFECTIVE COLLISIONS per SECOND) of a chemical reaction. We will finish explain the other factors tomorrow.
Our next exam is on Monday. The vacation assignment will be posted this weekend; you will be have a 100 point test on the assignment on the second day of our return from vacation.
Regents: we calculated the energy released or absorbed for several chemical reactions or physical processes listed on Table I.
We then varied the mole quantities and calculated a proportional change in the quantity of heat absorbed or released.
We then began to define and explain the three types of equilibrium: phase, solution, and chemical.
The vacation assignment will be posted this weekend; you will be have a 100 point test on the assignment on the second day of our return from vacation.
AP: We qualitatively calculated the relative temperature required for a spontaneous process depending on the signs of delta H and delta S for a reaction or process.
we calculated the entropy change for a phase change at the equilibrium temperature by noting that delta G is zero at such a temperature, so negative delta H divided by absolute T must equal the change in entropy for such a process.
We reasoned that the change in entropy for the vaporization of most molecules is about the same: 88 Joules per mol per K, Trouton's Rule.
We then discussed the importance of delta G STANDARD, emphasizing that delta G standard for a reaction MUST MAINTAIN concentrations of any aqueous reactant or product AT ONE MOLAR and any gaseous reactant or product AT ONE ATM pressure. Naturally, these conditions cannot be maintained as a reaction proceeds but delta G standard WILL tell us how a reaction will PROCEED (towards reactants or products) as a reaction proceeds towards the EQUILIBRIUM (NON-STANDARD) concentrations and partial pressures.
This is shown in the relation: delta G = delta G (standard) + RT lnQ
and, AT equilibrium, delta G = 0 = delta G (std) + RT ln K , which rearranges to delta G (std) = - RT lnK at equilibrium, of course. So, for a given reaction at a given temperature, since K is a CONSTANT, SO IS delta G standard !!!
Because we have no class this Friday, I will offer a "5 steps to a 5" review session on Thursday.
We then discussed two of the five factors that can AFFECT the rate (number of EFFECTIVE COLLISIONS per SECOND) of a chemical reaction. We will finish explain the other factors tomorrow.
Our next exam is on Monday. The vacation assignment will be posted this weekend; you will be have a 100 point test on the assignment on the second day of our return from vacation.
Regents: we calculated the energy released or absorbed for several chemical reactions or physical processes listed on Table I.
We then varied the mole quantities and calculated a proportional change in the quantity of heat absorbed or released.
We then began to define and explain the three types of equilibrium: phase, solution, and chemical.
The vacation assignment will be posted this weekend; you will be have a 100 point test on the assignment on the second day of our return from vacation.
AP: We qualitatively calculated the relative temperature required for a spontaneous process depending on the signs of delta H and delta S for a reaction or process.
we calculated the entropy change for a phase change at the equilibrium temperature by noting that delta G is zero at such a temperature, so negative delta H divided by absolute T must equal the change in entropy for such a process.
We reasoned that the change in entropy for the vaporization of most molecules is about the same: 88 Joules per mol per K, Trouton's Rule.
We then discussed the importance of delta G STANDARD, emphasizing that delta G standard for a reaction MUST MAINTAIN concentrations of any aqueous reactant or product AT ONE MOLAR and any gaseous reactant or product AT ONE ATM pressure. Naturally, these conditions cannot be maintained as a reaction proceeds but delta G standard WILL tell us how a reaction will PROCEED (towards reactants or products) as a reaction proceeds towards the EQUILIBRIUM (NON-STANDARD) concentrations and partial pressures.
This is shown in the relation: delta G = delta G (standard) + RT lnQ
and, AT equilibrium, delta G = 0 = delta G (std) + RT ln K , which rearranges to delta G (std) = - RT lnK at equilibrium, of course. So, for a given reaction at a given temperature, since K is a CONSTANT, SO IS delta G standard !!!
Because we have no class this Friday, I will offer a "5 steps to a 5" review session on Thursday.
# posted by C @ 4:29 PM 
