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  #1  
Old 02-21-2003, 09:31 AM
Moeman Moeman is offline
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Calcium Carbide

This is a two part question.


1.) What is the chemical formula for the combining of w2ater and calcium carbide?

2.) Would water+calcium carbide be stable enough to run through eletrolysis?

I am trying a home science experiment but don't want to get injured before trying it.
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  #2  
Old 02-21-2003, 09:34 AM
scm1001 scm1001 is offline
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CaC2 + 2H2O = C2H2 (acetylene) + Ca(OH)2

no, it will react with water immediately. I am not sure why you want to electrolyse calcium carbide?
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Old 02-21-2003, 09:37 AM
Q.E.D. Q.E.D. is offline
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CaC2(s) + 2 H2O(l) --> Ca(OH)2(aq ) + C2H2(g)

The gas product, C2H2 is commonly known as acetylene.
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Old 02-21-2003, 09:38 AM
Moeman Moeman is offline
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Calcium Carbide

This is a two part question.


1.) What is the chemical formula for the combining of w2ater and calcium carbide?

2.) Would water+calcium carbide be stable enough to run through eletrolysis?

I am trying a home science experiment but don't want to get injured before trying it.
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  #5  
Old 02-21-2003, 09:43 AM
Moeman Moeman is offline
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Quote:
Originally posted by scm1001
CaC2 + 2H2O = C2H2 (acetylene) + Ca(OH)2

no, it will react with water immediately. I am not sure why you want to electrolyse calcium carbide?

I was wanting to try to reclaim the calcium carbide from the water, but I cn see from the formula that it won't work. It would more than likely blow up.
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Old 02-21-2003, 12:11 PM
Duck Duck Goose Duck Duck Goose is offline
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Um...

Water plus calcium carbide is not only NOT stable--it is explosive.

IANA chemist, and I don't know what the chemical formula is for water + calcium carbide, but I'd say we're looking at a "do not try this at home" thing. Electrolysis involves water, right? Um...

http://www.howe.k12.ok.us/~jimaskew/msds/carbide.htm
Quote:
Special Fire Fighting Proc: DO NOT USE WATER IN CALCIUM CARBIDE STORAGE AREA, NO FOAM.

Unusual Fire And Expl Hazrds: NONE WHEN KEPT DRY. FLAMMABLE EXPLOSIVE GAS IS PRODUCED ON CONTACT WITH WATER OR MOISTURE.
Calcium carbide is the stuff they used to use in miner's lamps. Dripping water on the calcium carbide releases acetylene gas, which is then (cautiously) ignited, which makes a flame.

http://jchemed.chem.wisc.edu/JCESoft...LAMP/MOVIE.HTM
Quote:
An antique carbide lamp contains two chambers. The bottom chamber is filled with calcium carbide. The top chamber is filled with water. A dial regulates the amount of water that drips from the top chamber to the bottom. The two chambers are screwed together. Water drips onto the calcium carbide, forming acetylene gas. The gas is lit with a match.
Exactly what kind of experiment did you have in mind?

<< steps away from the computer, asbestos shield at the ready >>
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Old 02-21-2003, 02:21 PM
yabob yabob is offline
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From having done some caving a couple decades ago, I have some first hand experience with carbide. Yeah, carbide + water gives you acetylene gas and quicklime in very short order:

CaC2 + H2O -> C2H2 + CaO

The calcium carbide, as sold for miner's lamps, looks like blackish-gray gravel. It smells of acetylene because it tends to react with the moisture in the air.

Spent, you wind up with this wet quicklime slurry to get rid of. Hopefully, not still producing acetylene.

The reaction itself is not terribly energetic, but, as noted, the acetylene gas is very flammable, and to be treated with caution.

That doesn't stop people from doing stupid things with it. I know of a case where a couple bozos decided they wanted to see what it would be like if a whole couple of pounds of the stuff were used at once, and tossed it in the toilet on the grounds that if it got out of hand, they could flush it (that, in and of itself, displays a certain lack of understanding of the process). Well, they tossed a match, and COULDN'T flush it because the flames were too high to let them reach the toilet handle. Probably just as well.

A fringe benefit is that the stuff is good for starting campfires - pile the wet & soggy wood over some tinfoil or a tuna can full of carbide, and you can have the novel experience of getting your sputtering fire going better by pouring a bit of water on the carbide.

BTW, on the lamp description - most lamps actually have a striker wheel and a flint on the outer edge of the reflector, so you don't have to light it with a match. The technique is to hold your hand over the reflector, letting the gas accumulate, then rapidly palming the striker wheel while moving your hand away. With luck, the lamp goes "whoompf" and is lit.

Another topic for you to look up is "carbide cannons".
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  #8  
Old 02-21-2003, 02:29 PM
yabob yabob is offline
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Pardon me, I got that wrong:

CaC2 + 2H2O --> Ca(OH)2 + C2H2

is what actually happens. You get hydrated quicklime and acetylene.
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  #9  
Old 02-21-2003, 06:04 PM
bibliophage bibliophage is offline
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Welcome to the SDMB, Moeman. You accidentally started this thread twice. You usually need to hit the submit button just once, even if you get an error message the first time. I have merged the two threads because they both had useful responses.

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