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Topic: Problem of the week - 09/07/2012  (Read 36125 times)

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Offline Borek

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Problem of the week - 09/07/2012
« on: July 09, 2012, 07:44:27 AM »
When 1.000 g of a strong oxidizer A was dissolved in water, solution initially became wine red, but soon the substance decomposed, producing 85 mL (STP) of a dry gas B and 0.4032 g of a red-brown solid C. Drop of a concentrated, oxidizing acid, added to the alkaline filtrate, produced white precipitate D. Red-brown solid C was dissolved in a hydrochloric acid, and 1 g copper wire was put into the solution. After reaction ended, mass of the wire left was 0.8396 g.

Name all substances, write all reaction equations.


This one is not very difficult, call it a side product of my current work on the stoichiometry calculator  :P
« Last Edit: July 12, 2012, 04:33:44 PM by Borek »
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Offline Rutherford

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Re: Problem of the week - 09/07/2012
« Reply #1 on: July 12, 2012, 11:47:06 AM »
If I could think of a gass that has the molar mass 157.27g/mol.
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Offline Borek

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Re: Problem of the week - 09/07/2012
« Reply #2 on: July 12, 2012, 12:09:11 PM »
No idea where did you get 157 g/mol from?
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Offline Rutherford

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Re: Problem of the week - 09/07/2012
« Reply #3 on: July 12, 2012, 12:44:46 PM »
The number of moles of the gass B is 0.085/22.4=0.003795, and its mass is 1-0.4032=0.5968g. M=0.5968/0.003795=157g/mol.
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Offline Borek

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Re: Problem of the week - 09/07/2012
« Reply #4 on: July 12, 2012, 12:53:06 PM »
No, mass is off.
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Offline Rutherford

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Re: Problem of the week - 09/07/2012
« Reply #5 on: July 12, 2012, 12:57:16 PM »
I guess you mean that not the whole amount decomposed.
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Offline Borek

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Re: Problem of the week - 09/07/2012
« Reply #6 on: July 12, 2012, 01:30:00 PM »
Decomposition was stoichiometric and went to completion.
« Last Edit: July 12, 2012, 02:55:38 PM by Borek »
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Offline Rutherford

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Re: Problem of the week - 09/07/2012
« Reply #7 on: July 12, 2012, 04:09:23 PM »
Then why is the mass off?
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Offline Borek

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Re: Problem of the week - 09/07/2012
« Reply #8 on: July 12, 2012, 04:25:06 PM »
I see now that the wording is not perfect, but you ignored information about the filtrate.
« Last Edit: July 12, 2012, 04:35:50 PM by Borek »
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Offline Rutherford

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Re: Problem of the week - 09/07/2012
« Reply #9 on: July 12, 2012, 05:00:44 PM »
Oh yes, my mistake, sorry.
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Offline Borek

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Re: Problem of the week - 09/07/2012
« Reply #10 on: July 16, 2012, 05:20:06 AM »
Looks like week was not enough... Which most likely means nobody but Raderford even tried  :-\

Deadline extended, I am going to wait for another week.
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Offline Ann1234

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Re: Problem of the week - 09/07/2012
« Reply #11 on: July 23, 2012, 10:10:22 AM »
Quote from: Borek on July 16, 2012, 05:20:06 AM
Looks like week was not enough... Which most likely means nobody but Raderford even tried  :-\

Deadline extended, I am going to wait for another week.

Borek, is not that we are not trying...I actually tried 2 times (last was yesterday) but I got stuck finding the strong oxidizer.... :(
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Offline Borek

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Re: Problem of the week - 09/07/2012
« Reply #12 on: July 23, 2012, 01:17:32 PM »
Quote from: Ann1234 on July 23, 2012, 10:10:22 AM
Borek, is not that we are not trying...I actually tried 2 times (last was yesterday) but I got stuck finding the strong oxidizer.... :(

Unfortunately I am away, so I can't answer immediately - but perhaps if you will post what you tried and what you found, it will either wait for a day or two till I will be able to comment, or it will trigger comments from others. I think there are things that should be obvious, like the identity of the red-brown solid.

OK, if someone is trying, I am extending it for another week.
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Offline Ann1234

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Re: Problem of the week - 09/07/2012
« Reply #13 on: July 23, 2012, 06:41:40 PM »
okay....I think the red brown solid may be Iron (III) Oxide, and I found that solutions of Fe(OH)3 are wine red...but this hydroxide in water seems to be stable...so I got stuck again  :(
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Offline Borek

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Re: Problem of the week - 09/07/2012
« Reply #14 on: July 25, 2012, 01:47:50 PM »
Good idea about iron(III) - but it is not the original compound. Its a product of the original compound decomposition.
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