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Topic: Explaination for gravimeteric analysis experiement  (Read 5213 times)

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Offline chaneliman

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Explaination for gravimeteric analysis experiement
« on: March 07, 2008, 08:40:30 PM »
In an experiment to find the proportion of sulfate in a brand of fertiliser why was hydrochloride acid added to the filtrate  and why were drops of barium chloride added?  :)

Offline Arkcon

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Re: Explaination for gravimeteric analysis experiement
« Reply #1 on: March 07, 2008, 09:30:49 PM »
Can you write a couple of reactions for us?
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Offline chaneliman

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Re: Explaination for gravimeteric analysis experiement
« Reply #2 on: March 07, 2008, 09:33:41 PM »
Ba2+ (aq) +    So4 2+(aq)  = BaSO4(s)

Offline Arkcon

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Re: Explaination for gravimeteric analysis experiement
« Reply #3 on: March 07, 2008, 09:39:44 PM »
Great, now, how does a sulfate assay work again?  What were your other steps, not outlined in the description, that is.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline chaneliman

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Re: Explaination for gravimeteric analysis experiement
« Reply #4 on: March 07, 2008, 10:22:22 PM »
the steps are on http://resources.mhs.vic.edu.au/chemistry/year12/3pracproc.pdf its the first experiment

Offline chaneliman

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Re: Explaination for gravimeteric analysis experiement
« Reply #5 on: March 08, 2008, 06:52:42 AM »
my prac can be found at http://resources.mhs.vic.edu.au/che... , its this first and thrid prac (we're doing a combined prac, how fun).
Why does the precipitate need to be washed?
Why was an excess of barium chloride solution added?
Why must the precipitate be heated to constant mass?
List two reasons why barium sulfate is a suitable product in this gravimetric anaysis?

Also, i noe the observation part of the prac is usually one of the most easily parts to write, but for this prac i just don't noe wot 2 write. i mean there wasn't that much to observe except for the colour change and weight change, which is already in my results section. Wot do u think i should note? Thanks

Offline Arkcon

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Re: Explaination for gravimeteric analysis experiement
« Reply #6 on: March 08, 2008, 09:28:35 AM »
Kindly don't just link to online labs.  That hardly counts as work on your part.  FWIW, I've done gravimetric analysis in an industrial setting, so the setup is pretty trivial to me.  If you'd taken the time to paraphrase your procedure for us, you might have been able to answer some of your own questions.

As in your previous question, http://www.chemicalforums.com/index.php?topic=23221.msg88318#msg88318 there are little to no hints I can give you.  Either you've gleaned the basic concepts and specific facts outlined in your analytical chemistry text and class notes, or I'd just end up giving the answers away. For example ...

Why does the precipitate need to be washed?
Why was an excess of barium chloride solution added?
Why must the precipitate be heated to constant mass?
List two reasons why barium sulfate is a suitable product in this gravimetric anaysis?

Can you try to give some ideas for the first three questions?  Then, can you combine those answers into the answer for the last one?

Quote
Also, i noe the observation part of the prac is usually one of the most easily parts to write, but for this prac i just don't noe wot 2 write. i mean there wasn't that much to observe except for the colour change and weight change, which is already in my results section. Wot do u think i should note? Thanks

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Heh, OK, you also wanted to know why HCl was added to the filtrate.  What can you tell us about the properties of chlorides, in general?
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline Borek

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Re: Explaination for gravimeteric analysis experiement
« Reply #7 on: March 08, 2008, 11:38:58 AM »
chaneliman: in case you have not understood Arckon irony, please read forum rules. Point 5.
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