Here you can post your question(s) and hopefully get an answer:
Previous semesters: Fall 03,
Fall 05,
Fall 2007:
Q17(12/09/07): will
there be an equation sheet for the final...like the one for exam
1?
A17(12/09/07): As it says
on the schedule page, you prepare your own chit sheet - anything
you can fit on one page of regular A4 sheet of paper.
Q16(12/09/07): For the
photovotaic cell calculations; would the expected value be that
of the redox potential from the table or would we need to
consider the band gap value of Cu2+? Any ideas would be greatly
appreciated.
A16(12/09/07): You have to
speculate based on your findings. If you had just two metal
electrodes, would you observe the photovoltaic effect? or would
you expect it to be present? Please be careful and do not confuse
a voltage difference due to reduction potential difference of the
electrodes (battery) with that induced by light, i.e.,
thephotovoltaic effect.
Q15(12/08/07): Is the
extra credit, Photovoltaic cell, due the day of the final
(monday)...or can we bring it in later that week?
A15(12/08/07): It's due by
Wednesday, December 12.
Q14(11/20/07): -
Regarding the extra credit, are we allowed to work with a partner
when generating the photovoltaic cell? Or do we each have to
produce the cell and bring it into class along with the
calculations?? Happy Thanksgiving!! by the way =-
A14(11/20/07): Yes, you
can work with a partner on design and performing the experiment.
Each of you will present the data to me in person individually.
Q13(11/16/07): -
On-line quiz Quantum_numbers is due 11/17/07. Minimum 3 problems
....
Dr. Smirnov,
When looking at your grades on the website, it reads that we have
the quantum #s quiz due tomorrow(above). But on the schedule it
says that the quantum #s quiz is due on when we get back, I think
the 26th, with a minimum of 6 problems rather than 3. Which one
is right, or are they both due??
A13(11/16/07): Sorry, It
is 26th. Thank you for pointing out. I've fixed it. Have a good
Thanksgiving.
Q12(11/12/07): Hi
Dr.Smirnov,
Could you extend the deadline for exam 2 also? cuz I really
had a hard time to complete it.
I think I need more time to do and try to understand every
question.
Thanks!
A12(11/12/07): Sorry, It
won't be possible. It is an exam after all. I gave you the whole
weekend for it when you could ask your questions, if you had
some. Cheers.
Q11(11/11/07): Dr.
Smirnov I'm having a lot of trouble with #7. I looked at the
notes and it looks most like the slide on "Rapid equilibrium
followed by a limiting first order reaction". However, the
intermediate product is not a complex "PX" as given. I
thought the rate would be dependent merely on concentration
Fe2+(L)n; so I'm not really sure why we are expressing it as
total concentration of Fe, unless we can consider rxns 2 and 3
"independent". I'm pretty much out of ideas. Can you
give me any suggestions? Thanks!
I should note that I did try to use the idea that d([Fe2+]/dt)
= -k2[H2O2][Fe2+] - k-1[Fe2+][O2] k1[Fe3+][O2-], but I
couldn't figure out how to incorporate the idiea of total
concentration of iron. I promise I'm trying :) Just can't seem to
get anywhere.
A11(11/11/07): Do not
forget that [Fe]t = [Fe2+(L)n] +
[Fe3+(L)n]. Thus [Fe2+(L)n]
= [Fe]t - [Fe3+(L)n], and from
the quasi eqilibrium condition on the itermediate concentration,
you get the expression for the desired concentration in the
expression for the rate limiting reaction.
Q10(11/11/07): excuse
me being redundant, since Eo=0...does this mean dGr=0 as well?
thank you, this would clear things up quite a bit!
A10(11/11/07): Do you mean
that any reaction that does not involve charge transfer, would
have zero DGo? Since DGo = -nF Eo,
when n = 0, one cannot define Eo.
Q9(11/11/07): is there
a reduction potential for for the dissociation of water in #3?
...there appears to be no electron transfer so does this mean NO?
A9(11/11/07): Yes, you've
got it. There is no electron transfer - thus there is no Eo.
Q8(11/11/07): dr.
smirnov,
i am still confused as to you want me to correlate the value form
question 3 to obtain a new value in question 4. should i proceed
the same way in calculating deltaG 1st then deltaG prime? any
feedback will be appreciated. thank you
A8(11/11/07): There is no
'correlation' involved. If you can calculate D1Go
in any other way, go ahead. I am suggesting you a route where you
calculate it through a combination of DGo
for other reactions. I gave a list of reactions that would be
useful. Once you construct rxn 1 as a linear combination of these
reactions, you will see that rxn 6 would be necessary for you as
well.
Q7(11/11/07): Dr.
Smirnov, on question 1 am I using rxn 1 as the overall rxn to
identify the % ionization for the unbuffered, pH=7 and 1.
As far as question 4 is concerned, given that you want us to use
d6G from the previous rxn. should i calculate drG for rxn (1) via
a sumation of drG's leading up to the overall rxn any help that
you may be able to provide will be greatly appreciated. thank
you.
A7(11/11/07): Where in rxn
1 do you see salicylic acid? The question asks you to calculate %
ionization of salicylic acid in unbuffered water and in buffered
at two pHs.
Q4: Calculate DGo (and Eo) for reaction 1
using parameters for other rxns. Yes, you need to represent rxn 1
as a combination of other reactions and calculate the D1Go
accordingly.
Q6(11/10/07): Hello Dr.
Smirnov! Thank you for your help. I'm sorry but I also had
another question. On #4, I think I calculated Gibbs energy and
potential for the reaction (1) without any problem. However, I'm
confused as to what you mean when you say to calculate the
potential for reaction 3 as a "function" of the
potential for Fe.
Also, does it matter that Fe is bound to a ligand? Can we just
use the Fe3+-->Fe2+ value in the book?
I also noticed Reactions 1 and 2 "sum up" to reaction
3. Should that be included here? I'm sorry I'm just really
confused!
A6(11/10/07): The cell
potential in reaction (3) will obviously depend on the redox
potential of Fe(L)n3+, which dependson L, as it was explained.
The later question (#6) asks you to analyze the spontaneity of
rection 3, i.e. to use what you calulate for this question. You
are mistaken in stating that reaction (1) + reaction (2)=reaction
(3). It is actually reaction (1) = reaction (2)+reaction (3).
Good luck
Q5(11/9/07): Hi I'm
sorry to bother you, but I don't think I'm understanding number
one. In part two, you say it is a buffered solution at pH 7.
However, we know the pKa value is 3 (which is no where close to
7) and you specify 0.1M salicilic acid. But by plugging these
values into the henderson-hasselbach equation to find the amt. of
conjugate base that must be added to form the buffer, I get a
HUGE concentration. What am I missing here? Thanks!
A5(11/9/07): The purpose
of a buffer is to hold the pH. In this case, there is another
acid/base pair that holds the pH at the value of that pH.
Good luck
Q4(10/26/07): Dr.
Smirnov, I noticed that both HW10 and HW11 are due on Monday the
29th of October. Is this a mistake and only HW10 is due like
normal or is HW11 due Monday as well?
A4(10/27/07): Of course,
that was a misprint. I've fixed it. Thank for pointing it out.
Q3(10/04/07): Is there
heat exchange b->c?
A3(10/04/07): I presume
that the question refers to problem # 10 from the exam. If
pressure changes but not the volume then temperature should
change. From the first law and being able to evaluate work, you
can conclude what the heat exchange is.
Q2(10/04/07): Good
morning Dr. Smirnov, I noticed you were busy so i'll e-mail you.
I had a question to problem 10 on the take home section. Since
you did not lable T anywhere on the graph i am assuming this is
an isothermal expansion; however, surely some temperature change
MUST occur going B->C and D->A, my question was going from
A->B and C->D is there a temperature change?From your old
exam you have an adiabatic system and going from A->B/C->D
you have listed dU is zero and as an explanation because it's
isothermal. Does this mean there is a heat exchange with the
surroundings to keep sysem isothermal? Thanks for your time.
A2(10/04/07): Since this
is an ideal gas and the number of moles (one) does not change,
you can always calculate that temperature. There is no need to
presume anything.
Q1(08/30/07): I had a
question regarding my grade. It looks like I didn't receive full
credit for quiz 1 and the ideal gas equation quiz and I was just
wondering why. I completed both and I thought they were based on
effort not correctness.
A1(08/30/07): Topical
quizzes, like the Ideal gas one are graded based on the
performance prorated with respect to the maximum amount
(typically 2 points). For example, if you get 3 correct about of
4 total, the score will be 2 x 3/4 =1.5. You can always make that
a perfect score (and are encouraged to do so) in case you are not
satisfied with what you have by refreshing the screen of your
browser and starting again.
Weekly quizzes are currently not graded -
you get the point for participation. IN a near future, they will
be graded as well.
C1 (//07): T
Last updated on 12/09/07