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Bleach and Hydrogen peroxide?


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#1 Saturnine

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Posted 1 August 2009 - 06:43 AM

I learned on this forum that if one wants to neutralize bleach one can add hydrogen peroxide. Useful if one wants to clean up after a bleach spill or clear a washing machine in a laundromat with oxyclean before putting their clothes in. The post said that one gets salt, water, and oxygen.

My question, is this an endothermic, exothermic, or neutral reaction. Would it be safe to rinse ones hands in H2O2 after using NaOCl, or is one risking harm?
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#2 John Cuthber

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Posted 1 August 2009 - 05:30 PM

At high concentrations H2O2 will damage skin.
What's wrong with washing the bleach off with water?
A bit of lemon juice might help kill the smell of chlorine ( because vitamin C is a strong reducing agent and will remove chlorine)
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#3 UC

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Posted 5 August 2009 - 07:32 PM

I learned on this forum that if one wants to neutralize bleach one can add hydrogen peroxide. Useful if one wants to clean up after a bleach spill or clear a washing machine in a laundromat with oxyclean before putting their clothes in. The post said that one gets salt, water, and oxygen.

My question, is this an endothermic, exothermic, or neutral reaction. Would it be safe to rinse ones hands in H2O2 after using NaOCl, or is one risking harm?


Perhaps in theory, but bleach mixed with hydrogen peroxide will also make some chlorine gas.
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#4 bob000555

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Posted 6 August 2009 - 06:33 PM

It is more likely that the fallowing will occur then that it will yield chlorine.
NaOCL + H202 -> NaCl + H2O + O2
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#5 UC

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Posted 6 August 2009 - 10:01 PM

It is more likely that the fallowing will occur then that it will yield chlorine.
NaOCL + H202 -> NaCl + H2O + O2


Hence my use of "some."

If you intend this as a means to neutralize bleach, then the production of any chlorine gas is unacceptable. Go try it. I guarantee the fumes coming off are not just oxygen.
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#6 dr432

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Posted 7 August 2009 - 02:16 AM

i've tried it, it heated up only a bit and started bubbling although a lot less violently than say HCl and Bleach. i collected the fumes in a cylinder and it looked like pure oxygen with no smell of chlorine... although it might have had some bleach vapor due to the heat of the reaction.

it's a fairly exothermic reaction and yeah i guess it is a good way to neutralize bleach, if you don't mind the oxygen gas generated and perhaps some bleach vapor from the heat. there's no reason it would make any chlorine i mean you have 2 oxidizers obviously it would make oxygen.

Edited by dr432, 7 August 2009 - 02:26 AM.


#7 Theophrastus

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Posted 7 August 2009 - 06:14 PM

i collected the fumes in a cylinder and it looked like pure oxygen with no smell of chlorine... although it might have had some bleach vapor due to the heat of the reaction.


"...It looked like pure oxygen..." -I should note that both gases are colourless, and thus, you cannot expect to be able to visually distinguish between them.
No smell of chlorine? You actually went on to smell the gases produced, knowing the possibility of chlorine gas present? That's quite tactless. I assure you, there are far better ways to test for chlorine, than breathing its vapours. (Which by the way, in case you didn't initially know, are toxic!) I recommend you don't do something so foolish as smelling unkown gaseous products, unless you desire to suffer from associated health problems.

it's a fairly exothermic reaction and yeah i guess it is a good way to neutralize bleach, if you don't mind the oxygen gas generated and perhaps some bleach vapor from the heat.


Consider that the initial purpose of this method, was to neutralize any bleach, present on ones hands. Please re- evaluate your statement accordingly.

The reaction itself, is non- stoichiometric, taking two (or more) pathways simultaneously: (In this case it's 2, if you don't count the independent decomposition, of the two oxidisers)

 2NaOCl + H2O2 -> 2NaOH + O2 +Cl2

 NaOCl + H2O2 -> NaCl + O2 + H2O

I believe the first reaction pathway I noted, was the one UC was refering to.

Edited by Theophrastus, 7 August 2009 - 06:23 PM.

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#8 javagamer

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Posted 7 August 2009 - 11:52 PM

"...It looked like pure oxygen..." -I should note that both gases are colourless, and thus, you cannot expect to be able to visually distinguish between them.

I'm pretty sure chlorine is greenish-yellow, though that's only in high concentrations.
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#9 Theophrastus

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Posted 8 August 2009 - 12:32 AM

Well yeah, you're right, but I highly doubt that enough chlorine would be produced, in order to get the necessary high concentrations, to give it a visible, pale greenish- yellow tinge. In making my statement, I was speaking with pragmaticism in mind.
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#10 dr432

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Posted 8 August 2009 - 12:34 AM

theophrastus its really hard to read your posts you keep using really proper science and proper english. especially when you make errors in your judgement left and right.

2NaOCl + H2O2 -> 2NaOH + O2 +Cl2

this reaction will never happen just look at it, you have NaOH a basic agent and the acidic gas Cl2, i mean i'm surprised UC thought it would happen. and big deal with the chlorine i've smelled the fumes of bleach + HCl lots of times if you're not an idiot you'll turn away as soon as you smell it, i mean its real irritating smell but it won't harm you, sure if you inhale it directly you can get pulmonary edema or something serious like that...

Edited by dr432, 8 August 2009 - 12:42 AM.


#11 insane_alien

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Posted 8 August 2009 - 01:08 AM

this reaction will never happen just look at it


oh it will happen all right. try it and see.

chlorine itself is not acidic and it is released to the atmosphere where it couldn't react with the NaOH anyway.

also, chlorine was used as a chemical warfare agent in several wars. it IS harmful at all levels especially if there is repeat exposure.

i suggest you stop talking like you know something inside and out when you clearly have as much clue as a freshly lobotomized dung beetle.
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#12 dr432

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Posted 8 August 2009 - 01:11 AM

i'm not a chemist but i can say it will not happen theoretically or in real life. and i have tried it, more than once.

chlorine was used as a chemical warfare agent in several wars. it IS harmful at all levels especially if there is repeat exposure.


you can't compare a whiff of chlorine to how it was used in war. in war people were suffocated with it until it filled their lungs and they were coughing and dying from lung irritation. not a small irritating whiff which you can turn away from.

chlorine itself is not acidic and it is released to the atmosphere where it couldn't react with the NaOH anyway.


what i meant was not that those products would react back but that they wouldn't form in the first place because its less stable.
i mean sure as with every reaction will happen to some degree but no appreciable amount of chlorine will form at all.

Edited by dr432, 8 August 2009 - 01:50 AM.


#13 Theophrastus

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Posted 8 August 2009 - 01:55 AM

i mean sure as with every reaction there's some equilibrium but no appreciable amount of chlorine will form at all


I never meant that the production of chlorine gas, would have higher prevalence over that of oxygen, however, if you believe it shall only occur in insignificantly trace amounts, you are sadly mistaken.

you can't compare a whiff of chlorine to how it was used in war. in war people were suffocated with it until it filled their lungs and they were coughing and dying from lung irritation. not a small irritating whiff which you can turn away from.


I recommend you read this, particularly in regards to the section covering inhalation/ ingestion:

http://msds.chem.ox....H/chlorine.html

especially when you make errors in your judgement left and right.


If you are refering to the direction of the arrow, I believe you are confusing this with the following reaction, involved in sodium hypochlorite's initial production:

 2NaOH + Cl2 -> NaOCl + NaCl + H2O

i suggest you stop talking like you know something inside and out when you clearly have as much clue as a freshly lobotomized dung beetle.


Thanks Insane Alien; I second that notion.
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#14 dr432

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Posted 8 August 2009 - 02:07 AM

ok. go buy some bleach. and some hydrogen peroxide. collect the gas. get it an ir spectometry (or whatever its called idk).

this is the reaction we all know will happen:

NaOCl + H2O2 -> NaCl + O2 + H2O
and this is the one you're suggesting will also happen:

2NaOCl + H2O2 -> 2NaOH + O2 +Cl2

but in reality that second reaction will not occur in any appreciable amount.
just think about it, what is more favorable? water + salt + oxygen, or caustic soda + chlorine + oxygen?

you might as well say:

2NaOCl + H2O2 -> 2Na + H2 + 2O2 +Cl2
i guess that also makes chlorine.

Edited by dr432, 8 August 2009 - 04:00 AM.

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#15 bob000555

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Posted 8 August 2009 - 03:46 AM

I know Wikipedia isnít that reliable but according to wiki this method is used to generate oxygen in the lab: http://en.wikipedia....Redox_reactions

This does make sense as H2O2 often acts as a reducing agent in alkaline environments meaning that NaOCl would be reduced to NaCl and Ĺ O2. Chlorine gas is a damn strong oxidizer and itís going to take a lot more energy to liberate that then to liberate oxygen. If any chlorine is released itís not going to be any applicable amount.
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#16 dr432

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Posted 8 August 2009 - 04:13 AM

thanks bob

i think people just know that bleach is famous for being chlorine bleach, for having chlorine in it, and fear it for that reason

in reality the oxidizing power of bleach is really just from that oxygen
2NaOCl -> 2NaCl + O2
there's no reason to fear chlorine in bleach any more than you would fear it in table salt.

So basically Saturnine, that forum was right. It's safe to use H2O2 to clean bleach spills.
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#17 Sebbass69

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Posted 8 August 2009 - 04:23 PM

thanks bob

there's no reason to fear chlorine in bleach any more than you would fear it in table salt.


I think you may be correct in saying that the amount of chlorine generated is not of real concern, however, chlorine bleach is definitely more reactive, and more able to generate chlorine gas than table salt is. I wouldn't be so scared of mixing concentrated HCl with table salt, but with bleach that would be a whole different story. That and I would challenge you to eat a teaspoon of table salt, and then a teaspoon of bleach. Saying the two are equivalent is just not correct....
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#18 bob000555

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Posted 8 August 2009 - 08:04 PM

No one said NaCl and NaOCl where equivalent. All that was said was that NaOCl oxidizes by being reduced to NaCl + Ĺ O2. Really the only way to get chlorine from sodium hypochlorite is to liberate hypochlorous acid which can easily decompose the Cl2

Eg. NaOCl + HCl -> NaCl + HOCl
HOCl + HCl -> Cl2 + H2O

And thatís why mixing bleach and hydrochloric acid is a bad idea.
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#19 Theophrastus

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Posted 8 August 2009 - 08:51 PM

Given this persistent skepticism, I'm going to attempt to clear things up, by setting some basic examples. Your first problem, Bob (I would address dr432, but he has sadly disappeared- (gasp :o) the magic of moderation!) is that you believe that hydrogen peroxide, takes purely the role of an oxidiser, within a reaction, decomposing, and thus donating an oxygen atom to the reaction. Thus why when combined with sodium hypochlorite, produces oxygen gas, in this reaction:

 H2O2 + NaOCl -> H2O + NaCl + O2

To explain, why my second proposed pathway is taken, I'll begin with an example: bubbling chlorine gas through hydrogen peroxide. Based upon your hypothesis, the peroxide will eject its oxygens, and the products will be oxygen gas, and hydrochloric acid:

 H2O2 + Cl2 -> 2HCl + O2

If you are slightly more conservative, in your point, you might say that the chlorine will simply react with the aqueous medium, to form hypochlorous and hydrochloric acid, while the peroxide simply naturally decomposes:

 2H2O2 -> H2O + O2

 H2O + Cl2 -> HCl + HOCl

In regards to my first incorrect example, this reaction is definitely not the prevalent one, however, my second one is none more so, as it assumes (based upon your assumption) that the hydrogen peroxide is purely a bystander, and while the reaction with chlorine and water, will occur, the peroxide also partakes in the reaction. Why, you may ask? Due to the instability of the central oxygen to oxygen bond, the reaction will instead progress as so:

 H2O2 + Cl2 -> 2HOCl

This is the reason why this reaction will occur alongside the generation of oxygen gas; the breaking apart of hydrogen peroxide's central oxygen bond, to form hydroxyl- esque radicals. This is why, alongside the one I displayed above, this reaction will occur:

 H2O2 + 2NaOCl -> 2NaOH + O2 + Cl2

(Cheers?).

Oh? and FYI, in regards to your post on hypochlorous acid, you should note that hypochlorous acid is an oxidiser, as well as an acid (just like  HNO3 ), and as such will naturally, with exposure to light or heat, decompose to oxygen, and  HCl . This  HCl product can then react with present  HOCl , to form chlorine gas. While the equimolar quantities of  HCl make the reaction run 'til completion, its not necessary, in order to make a solution of  HOCl produce chlorine gas.

 2HOCl -> 2HCl + O2

Finally, to the OP, Saturnine, I apologise for all this irrelevant argument, however for practicality's sake you should probably just use John Cuthbert's method, which is, all that is required of it- it's simple and effective. :-)

Edited by Theophrastus, 8 August 2009 - 09:14 PM.

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#20 Saturnine

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Posted 11 August 2009 - 04:02 PM

Thank you everyone.

I did not expect to start a controversy, though it certainly helped to have such a thorough discussion.

That was quite a read for someone who got a C in his freshman chemistry class, and this is what I took away from it. Chlorine Bleach can be safely neutralized with hydrogen peroxide; however, it is not likely to be a good thing to do against ones skin. It is better to thoroughly wash ones hands and use a little lemon juice if the chlorine oder is bothersome. Even better to use gloves when working with strong household cleaners. It may be a good idea to put some oxyclean in the water before adding clothes at laundromats, or if you had used bleach in the previous load at home, to help prevent that annoying spotting one sometimes gets from residual chlorine bleach in the wash.

Thank you again.
Saturnine
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