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Topic: moles of electron problem  (Read 5207 times)

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Offline vmaggio

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moles of electron problem
« on: August 03, 2007, 01:17:54 PM »
aah what did i do wrong, this seemed like an easy straight forward question. but I got it wrong.


How many minutes will it take a current of 16.197 Ampères to deposit 64.138 grams of aluminum (26.981538 g/mol)?


heres what i did,

i used, n= It\F   

64.138\26.981538 = 2.3771mol Al

2.3771mol = 16.197t\96,485

solved for t and got = 14160.3 s

14160.3\60 = 236mins


what did i do wrong?
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Offline sjb

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Re: moles of electron problem
« Reply #1 on: August 03, 2007, 02:22:43 PM »
Seems reasonable from what you've put, what's the answer given?

708 minutes?

Perhaps you've forgotten for each mol of Al you'll need 3 mol of electrons?

Al3+ + 3e- -> Al

???

S
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Offline vmaggio

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Re: moles of electron problem
« Reply #2 on: August 03, 2007, 02:25:47 PM »
it doesnt give us the right answer   :(
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Offline sjb

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Re: moles of electron problem
« Reply #3 on: August 03, 2007, 02:29:54 PM »
OK, what is the answer given, perhaps we can work backwards ;)

S
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Offline vmaggio

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Re: moles of electron problem
« Reply #4 on: August 03, 2007, 02:55:33 PM »
it doesnt give me a right answer, it only says its wrong.


they are random online homework questions. so every time I hit submit, i get new questions. but once i get a similar problem ill post it.
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Offline enahs

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Re: moles of electron problem
« Reply #5 on: August 03, 2007, 04:27:04 PM »
Did you leave part of the question out? If you did not, it is a poor question. Deposit the Al on what? What kind of Al was it? As SJB hinted at, it could be Al3+, or it could be Al2+, Al+, etc.
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Offline vmaggio

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Re: moles of electron problem
« Reply #6 on: August 03, 2007, 04:40:56 PM »
no, I copy\pasted the exact question, its probably just my nutball professor, who knows. Ive been doing his online homework questions all day and I haven't come across that question or a similar question yet.
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Offline sjb

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Re: moles of electron problem
« Reply #7 on: August 03, 2007, 05:18:56 PM »
Seems you're not the only one, (see http://www.jiskha.com/display.cgi?id=1175345041), perhaps it's an s.f. issue - is your problem page publically accessible? (personally not going to do much now as it's nearly 22:30 ;) )

S
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