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Offline xstrae

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Stoichiometry question
« on: November 14, 2006, 09:53:24 AM »
Hi,

0.84g iron ore containing 'x' percent of iron was taken in a solution containing all the iron in ferrous condition. The solution required 'x' cc of a dichromatic solution for oxidizing the iron content to ferric state. Calculate the strength of the dichromatic solution.

Can someone please explain how to do this problem?

thanks

Offline Borek

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Re: Stoichiometry question
« Reply #1 on: November 14, 2006, 10:46:49 AM »
What about reaction equation?
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Offline xstrae

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Re: Stoichiometry question
« Reply #2 on: November 14, 2006, 10:59:03 AM »
It wasnt mentioned.

anyway, this is what I think it must be: Fe2+ + Cr2O7 --> Fe3+ + Cr3+
how do i do this??

Offline Borek

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Re: Stoichiometry question
« Reply #3 on: November 14, 2006, 12:14:35 PM »
You have it described, it doesn't have to "mentioned".

Balance it.

http://www.chembuddy.com/?left=balancing-stoichiometry&right=balancing-redox
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Offline xstrae

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Re: Stoichiometry question
« Reply #4 on: November 14, 2006, 12:22:39 PM »
6Fe2+ + Cr2+6 --> 6Fe3+ + 2Cr3+

now what?
and you have given me that link about 5 times already. I have almost mugged it up unknowingly! ;)

Offline Borek

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Re: Stoichiometry question
« Reply #5 on: November 14, 2006, 01:23:45 PM »
Now, as I understand the question, x is just a numerical value identical in both cases, but referring to different units. Setup an equation combining x% (hint: convert mass to moles) with x cc (hint: use second unknown, Cdichromate), solve for Cdichromate. If x cancels out, you have a numerical solution, If x doesn't cancle out, you have an equation for Cdichromate. In both cases question is solved.

and you have given me that link about 5 times already.

Start every time with balanced equation, you won't see the link again.
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Offline xstrae

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Re: Stoichiometry question
« Reply #6 on: November 14, 2006, 02:01:12 PM »
ok I got Normality of dichromate solution as 0.15N. is it correct?
thanks for your help.

by the way what is the chemical formula of the monosodium salt of oxalic acid?

Offline Borek

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Re: Stoichiometry question
« Reply #7 on: November 14, 2006, 04:04:36 PM »
ok I got Normality of dichromate solution as 0.15N. is it correct?

No idea. Perhaps someone else will have a time to check.

Quote
by the way what is the chemical formula of the monosodium salt of oxalic acid?

Start with oxalic acid formula.
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Offline xstrae

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Re: Stoichiometry question
« Reply #8 on: November 15, 2006, 10:55:49 AM »
oxalic acid - H2C2O4
sodium - Na

Quote
Perhaps someone else will have a time to check.

Please dont bother answering questions if you dont have time to complete it.

Offline Alberto_Kravina

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Re: Stoichiometry question
« Reply #9 on: November 15, 2006, 11:11:31 AM »
Quote
oxalic acid - H2C2O4
sodium - Na
Yes - exactly - and in your case a hydrogen atom is substituted with a Na+ Ion

Offline xstrae

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Re: Stoichiometry question
« Reply #10 on: November 15, 2006, 11:21:34 AM »
allright thanks.

Offline Borek

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Re: Stoichiometry question
« Reply #11 on: November 15, 2006, 11:34:47 AM »
Quote
Perhaps someone else will have a time to check.

Please dont bother answering questions if you dont have time to complete it.

OK - next time you will even not get a hint from me.
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Offline xstrae

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Re: Stoichiometry question
« Reply #12 on: November 15, 2006, 12:37:41 PM »
I didnt mean to be rude.. Maybe it was because I very badly wanted to learn to do the problem, it was just a bit irritating that you didnt care to check my answer. anyway, sorry on my part.

Offline Gerard

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Re: Stoichiometry question
« Reply #13 on: November 19, 2006, 10:17:02 AM »
Now, as I understand the question, x is just a numerical value identical in both cases, but referring to different units. Setup an equation combining x% (hint: convert mass to moles) with x cc (hint: use second unknown, Cdichromate), solve for Cdichromate. If x cancels out, you have a numerical solution, If x doesn't cancle out, you have an equation for Cdichromate. In both cases question is solved.

-Again the concept of dimensional analysis can be used here, if you have any problem with the chemistry question i suggest that you look at thier units first and try to find out how to cancell then out.. i suggest you read the book "Chemical Process Principles" by Felder for a thorough discussion on dimensional analysis...
and i would also like to suggest that please be humble in asking questions you see, try to solve the problem yourself first then post it here on how you solve it then let the prfessionals scan your solutions for mistakes...
remember if you wont try it yourself how will you learn, right?
thank you
keep it up
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