# HCl/Cl yields water and chlorine gas?



## kadriver (Jan 26, 2012)

Does this look right (I studied an example of another formula on you tube)?

2 hydrochloric acid plus 1 hydrogen peroxide equals water and chlorine gas:
2HCl + H2O2 = 2H2O + Cl2

I need to take a basic chemistry class.

Thanks - kadriver


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## Geo (Jan 26, 2012)

I've never noticed a chlorine smell when mixing hcl + H2O2. the hcl i use gives a strong vapor anyway, sometimes i can smell it through my respirator. the only time i can smell chlorine is when i add chlorine to hcl. not saying it doesnt but just that ive never smelled any. i would imagine that the O2 would react and cause hydrogen gas and oxygen.


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## samuel-a (Jan 26, 2012)

Kev

AP works differently.
Since HCl alone does not oxidize copper, H2O2 is added.

There are two steps to this reaction, as i know it:
H2O2 + Cu = CuO + H2O
2HCl + CuO = CuCl2 + H2O


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## publius (Jan 26, 2012)

Geo said:


> I've never noticed a chlorine smell when mixing hcl + H2O2. the hcl i use gives a strong vapor anyway, sometimes i can smell it through my respirator. the only time i can smell chlorine is when i add chlorine to hcl. not saying it doesnt but just that ive never smelled any. i would imagine that the O2 would react and cause hydrogen gas and oxygen.


Geo, IF you smell something while using a respirator there are three things may be going on...
1. The concentration of the substance in the air may be overwhelming the cartridge.
2. The cartridge may be spent and needs to be replaced.
3. The cartridge may not be designed to protect you from the substance in the air you are breathing.
A forth possibility is that the seal around the respirator cup to your face may not be intact (briefly)
In any event, Leave the area! Ventilate and then , then it is safe, return.

Some smart forum member has a line in his signature to the effect that hospitals and morgues are not pleasant places to visit.


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## kadriver (Jan 26, 2012)

Here is a post by Lou that describes digesting platinum using HCl and H2O2. In this post he says to,"boil to remove chlorine", which indicates that chlorine was produced by mixing HCl & H2O2.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=8742&p=82338#p82338

I am not trained in chemistry, but I have noticed some formulas floating around here & there.

I guess for my own amusement, I was trying to get the reaction produced by mixing hydrochloric acid and hydrogen peroxide, written out in a balanced equation showing the production of chlorine gas in the process.

I don't know if the formula that I put in this post is accurate or not - can anyone tell me if it is correct as written?

If the formula that I posted is incorrect, then please post the correct representation to show the reaction hydrochlric acid mixed with hydrogen peroxide.

It will help me to learn about basic chemical reactions and what happens when I mix these two chemicals together.

Thank you - kadriver


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## Geo (Jan 26, 2012)

2HCl + H2O2 = 2H2O + Cl2

2HCl + H2O2 = H2O + Cl 

according to wiki answers


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## kadriver (Jan 26, 2012)

Geo said:


> 2HCl + H2O2 = 2H2O + Cl2
> 
> 2HCl + H2O2 = H2O + Cl
> 
> according to wiki answers



Like I said, I am not a very chemistry oriented person.

But I think I remember (from high school 37 years ago) that a gas always has a 2 associated with it - O2, Cl2 etc...

If this is true (with respect to written representations of chemical gases), then the equation has to produce a chloride symbol with 2 chlorines = Cl2.

To get it to balance with this stipulation, then there has to be two waters and 2 chlorines.

The expression; 2HCl + H2O2 = H2O + Cl is not balanced - correct?

I am asking because I do not know.

kadriver


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## butcher (Jan 26, 2012)

First let me say I am no chemist, so this is just In my opinion or theory until I learn better.

Much depends on how much water is involved, basically concentration, for one thing, HCl by nature has most of its portion as water, also peroxide is also high in water content, I also feel chloride is not easy to change to chlorine, also how strong the peroxide.

Chlorine gas and water form hydrochloric acid and hypochlorous acid (type of bleach)

Cl2 + H20 --> HCl + HOCl

Then hydrochlorus acid decomposes to HCl + O, hydrochloric acid and oxygen,

HOCl --> HCl + O

Halogen halides are unstable reactive substances and depending on temperature form gases

Hypochlorous acids are weak acids, and dissaociate easily.

Lets say we have HCl (approximately 80% H20 in the acid) + 3% H2O2 (approximately 97 % water).
The (HOCl) (bleach) I assume quickly breaks down in solution, giving up it’s Oxygen, 

Now this solution is still is mostly hydrochloric acid and water, which some bleach has formed in solution, but quickly disassociated back to HCl and oxygen.

So here we see how an acid peroxide solution (dilute peroxide) can oxidize copper and dissolve it into HCl as copper chloride, also we see how it can momentarily try and attack gold which would quickly cement back to copper, and the bleach formed in solution is so diluted with water and is that much that basically gold is not dissolved in the reaction.

With stronger H2O2 say 30% hydrogen peroxide in a solution of HCl the bleach (HOCl) is much stronger and takes longer to disassociate, and may be forming almost as fast as it does, (my guess),

So now we have HCl and bleach in solution, and as we know this will dissolve gold, and several of the platinum group metals

Also here we have much more HOCl forming and changing back to HCL and oxygen, and depending on temperature the chlorine will gas off.

When dissolving gold we need that chlorine in solution not leaving as gas,
So heating the solution makes chlorine gas leave easier, as cold solutions hold gas easier than warm or hot solutions, which do not hold gases, 
to me this a double edge sword heating makes solution dissolve gold faster but also removes the gas we need, (it can also help to remove water if heated strong enough to concentrate the acid), a cold solution will not dissolve gold very fast as chlorine is not formed in solution as easily.

many times the reactions have a lot going on inside and the chemical formula's and equations may not really explain what all is happening inside, but these do give us a way to try and explain them or figure out what maybe or might happen in a chemical reaction.


Now I am no chemist, and so this reaction, and theory of it, may not be totally true, I am just learning so until I learn different this is my guess on what happens.

Maybe a real chemist will heck out this theory and find the holes in my thoughts.


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## samuel-a (Jan 26, 2012)

Steve explained it very well before:
http://www.goldrefiningforum.com/ph...56&p=123525&hilit=+i+don't+know+steve#p123521


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## lazersteve (Feb 6, 2012)

Here's some stuff from the web on the subject:

Science Madness on HCl and H2O2

Steve


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## samuel-a (Feb 7, 2012)

After reading the thread in the link (a good read btw).
Seems that the chemistry behind AP is much more involved, where both the oxygen and Cl/HOCl (which seems to be in equilibrium but at small conc') are reacting to oxidize metals... in turn, metals ions also catalyze the reaction further.... may also explain why it is so easy to dissolve Pt sponge in AP....

Do i make any sense here?


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