Sciencemadness Discussion Board

hydrogen and chlorine

bilcksneatff - 20-11-2007 at 12:58

Is it possible to combine H2 and Cl2 to form HCl gas? Or is it stupid and completely unsafe?

Phosphor-ing - 20-11-2007 at 13:52

It is possible, but...

http://en.wikipedia.org/wiki/Hydrogen_chloride

... messing with pure Chlorine gas is not in any way safe.

evil_lurker - 20-11-2007 at 14:21

Both chlorine and oxygen are very fond of hydrogen... put them together and its likely their relationship will kick off with a bang.

IIRC, the only difference is all it takes with chlorine is a little bit of light to initiate the reaction.

BromicAcid - 20-11-2007 at 14:37

Check out Tacho's attempt at combining elemental hydrogen with chlorine for a good read:

http://www.sciencemadness.org/talk/viewthread.php?tid=2154

As has been stated before it can be done, hydrogen readily reacts with chlorine in the presence of sunlight, explosively (or almost so). It is difficult to react the two at a controllable rate at the very least without having cylinders of H<sub>2</sub> and Cl<sub>2</sub>.

It is not stupid so much as it is inefficient and it is only as unsafe as your setup, however I would recommend against it unless you already had in your possession a setup to accomplish this and available tanks of hydrogen and chlorine. As for other methods to make HCl they are covered around this forum.

Best of luck though if you do decide to go through with this method :)

trilobite - 20-11-2007 at 19:03

Here's a preparation of dry HBr from elements:

http://orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv2p033...

Obviously you'd have to change the setup a bit.

bilcksneatff - 21-11-2007 at 04:13

Quote:
Originally posted by trilobite
Here's a preparation of dry HBr from elements:

http://orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv2p033...

Obviously you'd have to change the setup a bit.


Won't Cl2 replace Br in HBr?

2HBr + Cl2 --> 2HCl + Br2
Quote:
Originally posted by BromicAcid

It is not stupid so much as it is inefficient and it is only as unsafe as your setup, however I would recommend against it unless you already had in your possession a setup to accomplish this and available tanks of hydrogen and chlorine. As for other methods to make HCl they are covered around this forum.

Best of luck though if you do decide to go through with this method :)


Your saying that it's a bad idea to put the H2 and Cl2 into a chamber together, you have to slowly add them together.

Would exposing it to extremely dim light slow the reaction down?

[Edited on 21-11-2007 by bilcksneatff]

Nerro - 21-11-2007 at 04:42

Probably the heat from the reaction is enough to sustain the reaction at a pretty violent rate.

Using a torch-like apparatus should do the trick, you just have to find a way to cool the HCl gas somehow.

Isn't it more practical to just add sulfuric acid to NaCl and lead the HCl through conc. H2SO4? Works for me...

Pro's: Cheaper and safer
con: not quite as cool

bilcksneatff - 21-11-2007 at 07:47

I lile the H2 + Cl2 method because I can make both from NaCl solution by electrolysis. I think NaCl solution would be less expensive than the H2SO4 + NaCl method. If I would try to make HBr instead, I could make H2 and Br2 from NaBr.

solo - 21-11-2007 at 07:58

Quote:
Originally posted by Nerro
Probably the heat from the reaction is enough to sustain the reaction at a pretty violent rate.

Using a torch-like apparatus should do the trick, you just have to find a way to cool the HCl gas somehow.

Isn't it more practical to just add sulfuric acid to NaCl and lead the HCl through conc. H2SO4? Works for me...

Pro's: Cheaper and safer
con: not quite as cool


Is the purpose of channeling HCl through H2SO4 to dry the gas? since adding aquous HCl to sulfuric acid will produce HCl gas......?.........solo

bilcksneatff - 21-11-2007 at 08:06

Does chlorine dissolve in water? If it does, can I just bubble hydrogen through the Cl2 solution to get HCl?

Phosphor-ing - 21-11-2007 at 08:55

@solo Yes, the purpose of bubbling the HCl(g) through (conc)H2SO4 is to remove the last of the water.

bilcksneatff - 21-11-2007 at 11:18

Sorry about all of the questions, but would sodium bisulfate react with salt to form sodium sulfate and HCl?

NaHSO4 + NaCl --> Na2SO4 + HCl

woelen - 21-11-2007 at 12:21

This works, but it requires fairly strong heating (200 C or so).

bilcksneatff - 21-11-2007 at 12:30

Quote:
Originally posted by woelen
This works, but it requires fairly strong heating (200 C or so).


Guess it's not very practical, then.

Maya - 21-11-2007 at 13:48

....Does chlorine dissolve in water? If it does, can I just bubble hydrogen through the Cl2 solution to get HCl?....

Yes, Cl2 does dissolve in water, you will get a solution of chlorine as well as HCl but you will also get hypochlorous acid as well, HOCl

[Edited on 21-11-2007 by Maya]

[Edited on 21-11-2007 by Maya]

12AX7 - 21-11-2007 at 14:13

*Cough* he said hydrogen, a reducing agent.

You may have trouble with the hydrogen gas though. A platinum catalyst would certainly suffice to get it to react, although it seems odd to me that you might place a precious metal in an increasingly acidic, oxidizing and complexing solution like that...

Alternately, you can bubble the chlorine into a cathode cell, reducing it to chloride. Course you get more anode byproduct, which might be chlorine or oxygen or something to that effect.

Tim

[Edited on 11-21-2007 by 12AX7]

not_important - 21-11-2007 at 17:37

Chlorine + HCl + water is going to chew up platinum (or gold), I suspect that sparks or light in the blue-violet end of the spectrum is best; think mercury vapour lamp.

Keeping the H2 + Cl2 diluted with an inert (N2) gas might solve the explosion problem.

In a simple electrolysis cell the formation of NaOH is going to reduce the production of gaseous chlorine - see "chlorate cell". Industrial cells are designed to keep the NaOH from reaching the anode region, the diaphragm cell is the type of design best suited to amateur implementation. Wikipedia does a decent job describing the cells.

12AX7 - 22-11-2007 at 01:23

Ah yes, chlorine species don't reduce well under ordinary cathode conditions. Go figure!

Accident

chloric1 - 22-11-2007 at 10:15

Back in 2004, I constructed an electrolytic chlorine cell based on the use of saturated brine with HCl added. I did not have many amps and the chlorine evolved slowly. My attempt at separating the positive and negative electrode compartments was in vain. On disconnecting my clamps a spark was formed and a loud bang ensued. Ever since, I ALWAYS unplug power supply before removing clamps! Oddly no rupturing or other damage was noted. It seemed that the mixture actually imploded!:o Very strange the reaction of hydrogen and chlorine. Obviously this is not the way to obtain HCl but more importantly the reaction is more academic in its attributed.

[Edited on 11/22/2007 by chloric1]

franklyn - 22-11-2007 at 18:37

http://www.ucc.ie/academic/chem/dolchem/html/comp/hcl.html

http://encyclopedia.airliquide.com/Encyclopedia.asp?GasID=17
NOTE you must copy this URL and paste into the address bar

.

tumadre - 23-11-2007 at 02:48

A little off topic, but what would be the upper pressure limit for safely storing a styrometric mixture of hydrogen and oxygen.

I know it lignites at 530-585 C

so would it be safe to store it at a pressure where the gas molecules have as much energy as they do at 530 C and 1 atmosphere?

bilcksneatff - 23-11-2007 at 13:05

I was glancingat my book of elements, and I found this interesting:

"When additional refining is necessary, bromine gas is mixed with sulfur dioxide and forced up through a cylinder that has water running down the inside surface. The gasses react with the water to produce hydrobromic and sulfuric acids:

SO2 + Br2 + 2H2O --> 2HBr + H2SO4"

This is from http://www.ucc.ie/academic/chem/dolchem/html/comp/hcl.html

"When Chlorine Water, (i.e. a solution of Chlorine gas, in Water) in a flask inverted in a basin of the same liquid is exposed to bright sunlight, the Chlorine, is decomposed and a solution of Hypochlorous Acid, remains.

H2O + Cl2 ==> HCl + HClO

The Hypochlorous Acid, is not very stable and the solution readily decomcomposes, especially when exposed to sunlight, yielding Oxygen,

2 HClO ==> 2 HCl + O2"

[Edited on 23-11-2007 by bilcksneatff]

Jdurg - 23-11-2007 at 19:37

Quote:
Originally posted by tumadre
A little off topic, but what would be the upper pressure limit for safely storing a styrometric mixture of hydrogen and oxygen.

I know it lignites at 530-585 C

so would it be safe to store it at a pressure where the gas molecules have as much energy as they do at 530 C and 1 atmosphere?


I don't think there is ANY safe way to store a stoichiometric mixture of Hydrogen and Oxygen. Basically, you're asking if you can safely store a perfect chemically balanced mixture of a strong oxidizer with a fairly good reducer under pressure.

I just simply wouldn't try that at all. There's a reason why the space shuttles separate their fuel and oxidizers and don't store them premixed in one container.

Just think what would happen if somebody opened the valve on that container anywhere near a flame. Or, if you accidentally tried to use the tank as an "all in one flame source". :o

not_important - 23-11-2007 at 20:16

Quote:
Originally posted by Jdurg...
I just simply wouldn't try that at all. There's a reason why the space shuttles separate their fuel and oxidizers and don't store them premixed in one container.
...


While there are other reasons, as I recall the melting point of oxygen is some 35 degrees above the boiling point of hydrogen. Pumping slush can be difficult to do, and getting a uniform composition might prove difficult considering the differences in specific gravity.

evil_lurker - 23-11-2007 at 20:32

Or you had just a tiny bit of static electricity... or you had flashback... in that case you'd basically be dealing with a very large bomb... a bomb contained inside a steel container that would increase the power of the explosion and send shrapnel everywhere.

bilcksneatff - 25-11-2007 at 06:07

Can anyone confirm my last post?

woelen - 25-11-2007 at 12:07

Your last post in theory is correct, but for practical purposes, this is a really bad way to make HCl. It simply takes too long before all Cl2 has reacted, and it will be very hard to get it all reacted. HCl with remains of chlorine in it is not good at all for experimenting. The chlorine does disturb almost every experiment you intend to do with it. Yet another problem is that this only makes very dilute solutions. Solubility of chlorine in water is not that good, so you would need to supply chlorine at a very low rate, otherwise it simply won't react.