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#Post#: 2616--------------------------------------------------
Problem of the week-16/06/2013
DIR By: Michel
Date: June 16, 2013, 7:46 am
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We resume our Problem of the week series with quite an
interesting problem.
A chemistry amateur was playing around with chemistry
experiments. He was experimenting an electrolysis of a solution
containing 5.00g potash alum and 8.00g NaCl. He made some
observations as follows:
At the anode; a white compound A is formed and the anode is
consumed in the course of the electrolysis.
At the cathode; a brown substance B is deposited. He used
copper electrodes and a 3.00V battery for the experiment.
Other observations include:
The electrolyte slowly changed color from a colorless solution
to a green solution.
The white compound formed a green precipitate C when treated
with aqueous NH 3 solution. A clear colorless blue solution was
obtained when excess NH3 was added.
The white compound formed a yellow precipitate when reacted
with NaOH solution. This yellow compound reverts to the white
color after being left in suspension for about 30 minutes. The
yellow compound in suspension reacs with aq NH3 to form a blue
ppt.
Questions
Explain why the electrolyte turned green.
How many white compounds were formed in the electrolytic cell?
What are they? Identify A, B, and C and use appropriate
equations to justify your claims.
Solving this problem is not possible without some degree of
speculation and assumptions, so feel free to do so!
This problem is worth +20.
#Post#: 2634--------------------------------------------------
Re: Problem of the week-16/06/2013
DIR By: Michel
Date: July 13, 2013, 3:49 am
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any taker for this POTW?
#Post#: 2680--------------------------------------------------
Re: Problem of the week-16/06/2013
DIR By: Chris
Date: August 5, 2013, 5:54 am
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This is a really difficult problem
#Post#: 2687--------------------------------------------------
Re: Problem of the week-16/06/2013
DIR By: Michel
Date: August 6, 2013, 6:28 am
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--- Quote from: Chris link ---
>
> This is a really difficult problem
>
--- End Quote ---
Follow the problem step by step, then follow it up by posting
how far you've gotten. i could give hints when i see your
attempt.
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