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Topic: Drying  (Read 4919 times)

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Offline Rutherford

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Drying
« on: August 27, 2012, 01:25:17 PM »
What of the following substances: NaOH, H2SO4, P4O10 and CaCl2 can be used for drying:
a)CO2(g)
b)NH3(g)

How to determine this? Should the substances react or...
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Offline Arkcon

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Re: Drying
« Reply #1 on: August 27, 2012, 01:36:49 PM »
All of your options are common drying agents.  You should exclude the ones that react with what you're drying, or you wont have any left.
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Offline curiouscat

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Re: Drying
« Reply #2 on: August 27, 2012, 01:41:48 PM »
What do you understand by "drying"?
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Offline Rutherford

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Re: Drying
« Reply #3 on: August 27, 2012, 03:10:34 PM »
That's the problem, I don't know how to think about it. I only know that sulfuric acid is a good substance for dehydration, and NaOH can absorb CO2. I think that CaCl2 is good for dehydration, too.
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Offline Borek

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Re: Drying
« Reply #4 on: August 27, 2012, 03:37:36 PM »
If NaOH absorbs CO2, will any CO2 pass the scrubber?
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Offline curiouscat

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Re: Drying
« Reply #5 on: August 27, 2012, 03:52:25 PM »
This is drying

A.H2O + Dessicant  :rarrow: A + Dessicant.H2O

If this happens, forget drying, you just destroyed your feed:

A + Dessicant   :rarrow:   Foo  

PS. Don't take my A.H2O too literally. I don't want to imply any compound formation nor stoichiometry. Often, water to be dried is just a mixture.
« Last Edit: August 27, 2012, 04:05:48 PM by curiouscat »
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Offline curiouscat

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Re: Drying
« Reply #6 on: August 27, 2012, 03:55:43 PM »
Quote from: Raderford on August 27, 2012, 03:10:34 PM
That's the problem, I don't know how to think about it.

One way to help you "think" is to indulge in the Socratic procedure. So try answering the simpler sub-questions no matter how silly they might seem.

So again: What do you understand by "drying"?
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Offline Rutherford

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Re: Drying
« Reply #7 on: August 27, 2012, 03:58:11 PM »
So, NaOH is bad for carbon-dioxide.
CO2*H2O is the acid. Sulfuric acid could be maybe used for this one.
NH3*H2O is a base, NaOH could be used.
What about the rest?
Drying-losing water probably.
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Offline discodermolide

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Re: Drying
« Reply #8 on: August 28, 2012, 12:05:32 AM »
Quote from: Raderford on August 27, 2012, 03:58:11 PM
So, NaOH is bad for carbon-dioxide.
CO2*H2O is the acid. Sulfuric acid could be maybe used for this one.
NH3*H2O is a base, NaOH could be used.
What about the rest?
Drying-losing water probably.


Drying is not just restricted to water, although the word implies removal of water. Generally it is the removal of volatile components from a material, usually solids. For example, if you crystallise something from cyclohexane, you then remove the cyclohexane from the solid by "drying".
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Offline Rutherford

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Re: Drying
« Reply #9 on: August 28, 2012, 04:32:32 AM »
Okay. I realized now that Ca reacts with H2CO3 and not with NH4OH so it can be used for NH4OH. Only the phosphorus oxide left.
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Offline mamid

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Re: Drying
« Reply #10 on: August 28, 2012, 08:15:43 AM »
Quote from: Raderford on August 28, 2012, 04:32:32 AM
"Ca reacts with H2CO3"
Only you don't have metallic Ca, but a Ca2+ salt. A completely different thing.
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Offline Rutherford

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Re: Drying
« Reply #11 on: August 28, 2012, 08:19:31 AM »
I meant that.
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