Chemical Forums
Chemistry Forums for Students => Inorganic Chemistry Forum => Topic started by: jray on January 08, 2008, 08:56:09 AM
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And the last problem i want you to advise:
1.9 g of a metal was electrodeposited on the cathode, when electrolysis of the salt of this metal (III) was carried out for 1.5 hour and electric current was 1.8A. Identify the metal.
I couldn't understand one thing, that this is practical mass and i need to find theoretical, but there's no current efficiency and i don't know how to find it. If i had that i could find it, by the formula:
m=E*J*t/96500 and when i calculate E of the metal i can identify it by multiplying by it's valance. So could you help my finding theoretical mass?
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Assume 100%.
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So it can't be 1.9 - 100 or am i missing something
x - 100
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Dear Jray ;
I believe your problem requires a little different recipe to be solved then yours.
Assuming 100% current efficiency you have to find out (calculate) how many moles the 1.9 g deposited metal are to determine its Atom Mass (AM), and then consult the Periodic System to identify your unknown ( = find the element with the nearest AM).
I found a final difference of 1.3% in AM by calculation.
So the recipe looks like:
- 1.) Determine how many mole electrons you spent during 5400 sec (= 1.5h).
(Remember: 1 A = 6.241 * 1018 electrons / sec; and 1 mole = 6.02214 * 1023 ) - 2.) Divide the number of mole electrons you found by 3, because:
Me+3 + 3e- -----> Me°
Now you have found the number of moles that deposit 1.9g of your unknown metal. - 3.) I think the small rest to find its AM can now be left to you.
I hope this small recipe is clear enough to be easy followed.
Good Luck!
ARGOS++