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Topic: Ionic mobility question  (Read 2763 times)

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Offline Danial

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Ionic mobility question
« on: October 16, 2010, 12:08:23 AM »


For part i, i used t+=u+/(u+ + u-)
and got 8.6 x 10-8
which is not equal to the u value in my book.
Is that method of finding the answer correct?

for all of part ii all my answers were kind of high
for part a
i used

conductivity at infinite dilution = (z+) (u+ +u-)F
and then found the conductivity at infinit dilution,
the i used the linear expression for conductivity
conductivity = limiting cond + k rootC
and im not sure what to use as k in this question, would it just be 1?

for part ii b
i used the same formula as in part i and found t
then used that t to find I+ using t = I+/I
then found lamba naught the molar conductivity and inifite dilution using lamba0 = Z+Fu+
then with that
i found E by rearanging
lamda0 = I/(ACE) and found E = 79840 which is huggee but the units are consitant
then in part C i found V = lE and the length was 0.01 so i got V = 798 which is also huge
then for part c i found using s = uE
that it moved 3.75m's in 10minutes, which is heaps haha

is my process correct in any way?
my answers seem way too high
thanks in advance

Offline Stclair

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Re: Ionic mobility question
« Reply #1 on: October 16, 2010, 08:32:14 PM »
I think for part b, you would be expected to get the correct value,
And the rest i'm not sure why but those voltages are huge maybe its a unit error

Offline Danial

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Re: Ionic mobility question
« Reply #2 on: October 17, 2010, 05:55:58 AM »
How else could i go about getting the correct value?

Offline Danial

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Re: Ionic mobility question
« Reply #3 on: October 17, 2010, 08:33:28 AM »
I found the error in part II b, i had to convert M into mol/m^3
now i have a more realistic volt meter and the rest of the answers seem nicer too.
but for part II a im trying to use the linear expression for molar conductivity, but i dont know what to use as the constant next to root concentration. In an experiement we did the K=-0.0003 but i dont think im supposed to use that in this question,
Could anyone give me a hint in solving that question?

Also with part i, ive done it like 4 different ways with different formulas and the answer isnt = to the literature value, maybe my lecturer just put a incorrect transport number so we wouldnt just look up the answer in the book
« Last Edit: October 17, 2010, 08:50:23 AM by Danial »

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