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barbs09
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Hi all, a simple question that probably belongs in “Beginnings” but is not worthy of a new thread..
Stupidly I have been using stichometric calculations for chemical synthesises without taking the water molecules on some hydrates into consideration.
This suddenly explains my low yields 
When working out a theoretical yield of a reaction using, for example, copper sulphate pentahydrate as a reactant, should I do my molar calculations
based on the anhydrous sulphate (159.62 g/mol) then correct for the extra H2O or start out using a combined molar mass of the pentahydrate which is
249.62 g/mol (159.62 g/mol CuSO4 + 90.08 g/mol H2O (5 x 18.016)).
Any help would be appreciated.
Cheers
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sparkgap
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Quote: Originally posted by barbs09  |
When working out a theoretical yield of a reaction using, for example, copper sulphate pentahydrate as a reactant, should I do my molar calculations
based on the anhydrous sulphate (159.62 g/mol) then correct for the extra H2O or start out using a combined molar mass of the pentahydrate which is
249.62 g/mol (159.62 g/mol CuSO4 + 90.08 g/mol H2O (5 x 18.016))
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Well, you really should just use the molar mass of the hydrate of whatever salt you're interested right from the start. The "correcting" you speak of
looks to be a more error-prone procedure to me.
sparky (~_~)
"What's UTFSE? I keep hearing about it, but I can't be arsed to search for the answer..."
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sakshaug007
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| Quote: Originally posted by Nicodem | | Lithium perchlorate can and is commonly used as electrolyte in organic solvents. It is soluble in all solvents that are at least slightly basic,
including acetone, and it does not get destroyed by oxidation at the anode like NaCl (which is not soluble in acetone anyway). But where did you saw
acetone can be used as solvent? I would imagine methanol or something like that, but not acetone which reacts at both electrodes.
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I actually didn't see that it can be used as a solvent in this case I'm simply trying it because I don't have any other polar aprotic solvents at the
moment (I am going to get DMSO pretty soon though). You said that acetone reacts at both electrodes what does it produce? I was able to dissolve a
significant quantity of LiCl in acetone (0.35g/100ml) when I attempted the electrolytic deposition of lithium. It did work, lithium was deposited on
the cathode as black amorphous powder which reacted violently when dipped into water, and likewise chlorine was produced at the anode (graphite
electrodes were used). By the way would other perchlorates dissolve just as well such as ammonium perchlorate, or sodium perchlorate?
Thanks for the reply.
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bquirky
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| Quote: Originally posted by sakshaug007 | Hello everyone,
I am going to attempt the electrolysis of chloroform in acetone solvent, and I wanted to ask what ionic salts you would suggest for an electrolyte,
(i.e., readily soluble in acetone). I understand that I can just use a small amount of NaCl but if I end up doing a lot of this in the future I would
prefer a salt that can dissolve in higher concentrations in acetone.
Thanks a lot. |
Hi ive done some playing around with zinc chloride in acetone
it plates out but a zinc anode should replace the zinc in solution
I have also used aluminium chloride in ethanol which plated out aluminium on the cathode as well (it fizzed in NaOH)
Sodium chloride dosnt seem to dissolve well in any organic solvent that i have been able to try (not many)
Ive messed around with oxalate salts but my results where highly varied i think the oxalate may have been braking down
NaOH seems to dissolve in ethanol there is some conductivity im not sure if that might be usefull for you
On a separate note does anyone know if electrolisis can be used to strip water from organics to make esters ? perhaps in the presence a very small
amount of h2so4 with electrolisis simply removing the water from the sulfuric acid ?
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marksev1
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Hello i would need to know where to download some handbooks useful for searching physico-chemical data..i already have CRC handbook of chemistry and
physics, Lange's handbook,International critical tables... i would especially like to have Atlas of spectral data and physical constants for organic
compounds, if somebody knows where to find it....
What would you suggest for searching data such as solubility, i would need the most maybe for various natural products.. thanks for the answers!
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barbs09
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Thanks sparky, sounds good to me
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kclo4
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sakshaug007, perhaps Sodium Iodide? I remember that it is more soluble in acetone then the other sodium halide compounds.
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Panache
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Sodium Iodate
3 I2 + 6 NaOH → NaIO3 + 5 NaI + 3 H2O
Dehydrate this and heat to around 500C to decompose the iodate to NaI, i guess it would evolve oxygen (wow i'm really insightful today).
Question. Is NaIO3 'explosive' like the MSDS's and similar such information sources proclaim or is this process rather benign.
Is there a more practical route to NaI from KI than liberating the element and doing as i propose?
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Picric-A
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@ Panache- Release HI from the KI using conc phosphoric acid, and run the vapours through a NaOH or Na2CO3 soloution.
Now my question, im having trouble making 4-Aminobenzoic acid from polystyrene. I have managed to nitrate the polystyrene (i think) by dissolving the
polystyrene in dichloromethane then nitrating this mix using the normal HNO3/H2SO4 mix.
What im left with is a yellowish powder which is insoluble in water. The next step requires me to oxidise the polymer bond forming a methyl group. I
plan on oxidising this with with alkaline KMnO4. The problem i am facing is the nitropolystyrene does not dissolve in the oxidising mix and so nothing
happens.
Does anyone know what i can do to mend this problem, eg, what solvent can i dissolve it in to oxidise it?
thanks,
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DJF90
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I would suggest acetone. PS dissolves in it like a treat so I would expect nitrated polystyrene to also. However you may have compatibility problems
with the alkaline permanganate.
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panziandi
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Prolonged refluxing! As you begin to break the C-C polystyrene backbone to form the carboxylic acid it will dissolve in the alkaline solution. It will
be a slow reaction requiring prolonged and vigorous conditions, go figure!
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Panache
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| Quote: |
I just seen on How its Made of them using some chemical to etch the stainless steel with a picture of the maker, Any idea of what was used? He put the
chemical on a sponge and just pressed if for a few seconds and it etched the SS. Im thinking acid but im woundering if anyone has a more definitive
answer.
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HBr etches stainless quite effectively and quickly and is much safer than HF.
Does anyone know why the density vs concentration tables for h3PO4 solutions stop at 40% concentration of the acid?
Can tungsten be considered the equivalent to tantalum wrt using it for the wire in a whip stirrer or is it far less inert?
[Edited on 2-4-2009 by Panache]
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sakshaug007
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Does anyone know if acetone is a suitable solvent for carrying out non aqueous electrolysis reactions? i.e. doesn't oxidize or reduce. My experience
with it thus far has shown it to be pretty stable, I electrolyzed LiCl in acetone to produce black amorphous lithium metal and chlorine using graphite
electrodes then again I'm not sure if I produced lithium-acetone compounds as well. If acetone does undergo oxidation/reduction in an electrolytic
cell what does it form? Is it dependent on the electrolytes? Any advice would be great.
Thank you very much
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sparkgap
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Two questions from me:
1. A Fries arrangement will work for diphenyl carbonate and diphenyl oxalate, correct?
2. Would the conditions for hydrogenolysis of a benzyl group reduce double and triple bonds too?
sparky (~_~)
"What's UTFSE? I keep hearing about it, but I can't be arsed to search for the answer..."
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Sedit
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I have been looking into Phosphorus preperation and I happen to come across this while looking for something else..
How valid is this?
| Quote: |
Copper Carbonate, artificial malachite.
Cu2(OH)2CO3, toxic, green powder which is soluble in acids and decomposes at 200 C; used in pigments and pyrotechnics and as a fungicide and feed
additive; antidote for phosphorous poisoning. |
If true and it will stop phosphorous poisoning then how would one administer it?
I dont plan on ever getting phosphorous poisoning but its always good to have a backup plan, I didnt plan on choping my finger tip off either but shit
happens.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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Sedit
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LOL for reasons such as this.....
I recently made sodium nitrite from Pb and sodium nitrate. Thru out the whole time around it I was wearing latex gloves and being extreamly careful
and yet I started to get a metalic taste in my mouth. I dont really know how I contacted the Pb but the only thing I can think of is that the vapors
that came off where more then organic. The lead has been setting outside for years now and was once used as old plumbing pipe so was naturaly quite
cruded up before melting and skimming.
My question is what are the detection limits of the PbO or elemental Pb. If a metallic taste is had is that a sure fire sign that Im screwed or should
I relax a little bit more?
I was being very careful in ever aspect I could think of from gloves to working on wet news paper to keep dust levels down. I did not have a mask on
but I would next time. Should I be very concerned or give it some time. No ill effects are felt just an annoying slight metallic taste.
And what if any Pb could have volatilized from the dirty lead?
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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not_important
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See http://tinyurl.com/cawym4 for a 1908 take on this, from Google books.
Usually a solution of CuSO4 was used, but a suspension of the 'carbonate' would work. The stomach is washed out with the copper solution/suspension,
insoluble and fairly unreactive copper phosphide being formed. Similar solution can be used to treat phosphorous burns, preventing bits of
phosphorous from remaining in the wound to reignite on exposure to air, or to diffuse into the body. Again, just the first step in the treatment,
good cleaning of the wound is needed as well as other treatment.
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Sedit
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I like the idea of the turpentine antidote since it stated that some one was able to drink phosphorous followed with turpentine.
Thanks for that paper not_ since then I started drinking alot of milk as it talk about for heavy metals and metallic taste is pretty much gone.
Still a little nervous for good reason but should be a problem.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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smuv
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Preparative TLC Plates for Analytical Work
For a good price I can get some 2000 micron silica TLC plates; I have no desire to use these plates preparatively, but wonder if they would work out
ok for analytical work? I assume I would just need to spot a little bit more material onto the plate? Also is the thicker silica layer more prone to
flaking and cracking?
Thanks in advance; sorry if my questions are a little mundane; I just don't want to waste my money.
"Titanium tetrachloride…You sly temptress." --Walter Bishop
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Nicodem
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Preparative plates are not really suitable for your needs. I would really think twice before buying them unless they are really, really cheap. It is
not so much in that they are less suitable for analytical size of samples, but in that they are most commonly made on glass plates and cutting them
without damaging is a challenge in itself. They are used as a whole plate with the sample distributed along the entire starting line and are therefore
not made on a thick aluminium foil support like the analytical ones which can be cut with a knife. Also, a package of preparative TLC plates contains
much less plates (maybe 10 utmost) than the normal TLC package which usually contains 25 foils (20×20cm), where each foil can be cut to 1/3 lines (so
if you use ~1cm wide TLCs you can make approximately 3×25×20=1500 TLCs!).
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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Aubrey
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noob question (as alwys)
I attempted the reduction of cylopentanone using Al Isopropoxide. I have a black tarry substance in my flask which stinks on warming and i am afraid
of reheating it up until i buy a fume hood to recover my product, because last time my neighbours smelt gas and called out the gas men, this is even
wih placing a tube from the vacuum outlet into liquid.
Having said that, my question is, which other reducing agents may I use that are more pleasurable to work with?
Would I do better to look at synthing LaH?
many thanks
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Paddywhacker
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Did you have a reasonable excess of isopropyl alcohol?
Not too much water?
Not too high a pH? Ketones are notorious for giving tarry gunk with alkali.
Bad neighbours are a real nuisance, best dealt with by educating them. Maybe tell them that you are running an alcohol still. That will cover for
the occasional smell.
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dann2
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Hello,
Sorry to butt in (but you always have to butt in when asking a question in ' The Short questions' thread), but can someone sort out the following for
me.
Plating equations for Lead Dioxide (Lead Nitrate bath)are:
[1] H<sub>2</sub>O --> OH<sub>ads</sub> + H<sup>+</sup> + e<sup>-</sup><br>
[2] Pb<sup>2+</sup> + OH<sub>ads</sub> --> Pb(OH)<sup>2+</sup> <br>
[3] Pb(OH)<sup>2+</sup> + H<sub>2</sub>O --> PbO<sub>2</sub> + 3H<sup>+</sup> +
e<sup>-</sup>;<p>
giving an overall equation of:
Pb(NO<small>3</small> <small>2</small> +
2H<small>2</small>O =====>> PbO<small>2</small> + 2HNO<small>3</small> + H<small>2</small>
How many electrons in involved in the overall equation.
It has to be two (surely) for the two Hydrogens that are escaping at the cathode?
So I should put "+ 2e<sup>-</sup> " at the end of the overall equation.
My electrific chemistry knowledge is a bit horrific.
TIA,
Dann2
[Edited on 7-4-2009 by dann2]
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sparkgap
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| Quote: |
H<sub>2</sub>O → OH<sub>ads</sub> + H<sup>+</sup> + e<sup>-</sup>
Pb<sup>2+</sup> + OH<sub>ads</sub> → Pb(OH)<sup>2+</sup>
Pb(OH)<sup>2+</sup> + H<sub>2</sub>O → PbO<sub>2</sub> + 3H<sup>+</sup> +
e<sup>-</sup>
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(wait, does the "ads" stand for adsorbed?)
Well, if you put all three together and remove common species from the left and right sides, you should be getting...
| Quote: |
Pb<sup>2+</sup> + 2H<sub>2</sub>O → PbO<sub>2</sub> + 4H<sup>+</sup> +
2e<sup>-</sup> |
Here's your kicker: will nitrate ion be reduced under the conditions?
sparky (~_~)
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dann2
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Thanks for that Sparkgap,
The original stuff can be seen attached.
Two moles of Nitric acid are formed and two moles of H are released (I presume).
I have been kicked by your kicker..........
Nitrites (by reduction of Nitrates I presume) do build up in the plating tank. How much I do not know. Would small Cathode area's help to stop this
happening?
Cheers,
Dann2
Attachment: Journal of The Electrochemical Society, 149 (9) C445-C449 (2002).mht (9kB)
This file has been downloaded 975 times
[Edited on 7-4-2009 by dann2]
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