Cou
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Help with stoichiometry of a complex reaction: sulfuric acid and bleach
This is the website I read: http://www.ehow.com/about_6521382_sulfuric-acid-chlorine-ble...
The reaction between H2SO4 and NaClO has many middle steps, but this kind of reaction stoichiometry is out of my knowledge. How can I find out how
much 98% sulfuric acid I need to completely react with a given amount of 8.25% bleach? And is the gas pure Cl2?
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blogfast25
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Not really. Search for it on this forum, there are much better ways to prepare chlorine.
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Brain&Force
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Why don't you want to use HCl for making chlorine? It's a lot more efficient.
And I wouldn't trust eHow for chemistry at all...
At the end of the day, simulating atoms doesn't beat working with the real things...
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blogfast25
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What do you mean? It's Chemistry 101! 
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Cou
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Quote: Originally posted by Brain&Force  | Why don't you want to use HCl for making chlorine? It's a lot more efficient.
And I wouldn't trust eHow for chemistry at all... |
Even 31% HCl vs 98% H2SO4?
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Metacelsus
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Yes, it will give a cleaner product. Acidifying hypochlorite salts gives hypochlorous acid, which will react (comproportionate) with hydrochloric acid
to form chlorine gas. Without chloride ions, a substantial amount of Cl2O may be formed, which will eventually decompose into chlorine and
oxygen.
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Cou
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| Quote: Originally posted by Cheddite Cheese | | Yes, it will give a cleaner product. Acidifying hypochlorite salts gives hypochlorous acid, which will react (comproportionate) with hydrochloric acid
to form chlorine gas. Without chloride ions, a substantial amount of Cl2O may be formed, which will eventually decompose into chlorine and
oxygen. |
Oooo... Hope that Cl2O isn't a carcinogen. I didn't get exposed to more than 20 PPM, even while not wearing my respirator.
[Edited on 19-2-2015 by Cou]
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subsecret
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I use TCCA and 31% HCl to make chlorine. For most purposes, run the gas through a tube stuffed with cotton or fiberglass, which should trap acid
mists.
Fear is what you get when caution wasn't enough.
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Darkstar
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In bleach, Cl2, HClO and ClO- are all in a sort of pH-dependent, three-way equilibrium with one another. When the pH is low,
Cl2 dominates. When the pH is high, like your bleach, it's primarily ClO- ions. When the pH is closer to neutral, HClO forms.
Since HClO and HCl are in equilibrium with Cl2 and H2O, adding additional protons using an acid shifts the equilibrium towards
Cl2 production. The beauty of using hydrochloric acid is that you're not just adding more protons, but more chloride ions, too.
HClO + HCl ⇌ Cl2 + H2O
If you want the more technical version, HCl is the better acid because HClO is also in equilibrium with Cl2O. When you add an acid to
bleach, the first thing that happens is the ClO- ions get protonated to give HClO. If the HClO is protonated a second time, it's then
activated for nucleophilic attack on its chlorine. If a chloride ion attacks, Cl2 and H2O are produced. However, if the oxygen
on another HClO/ClO- molecule attacks, H2O and Cl2O are produced instead. By using HCl, you are adding a bunch of
chloride ions, greatly increasing the probability that it will be a chloride ion that ends up being oxidized.
In my opinion, though, HCl + TCCA (trichloroisocyanuric acid. can be purchased in bulk quantities from pool supply stores) is a FAR superior method
for Cl2 production.
Probably because you see things like this:
| Quote: |
In water solutions, hypocholorite (HClO) and chlorine (Cl2) reach an equilibrium that is dependent on the pH of the solution. In an acidic solution,
the equilibrium favors chlorine in the following fashion: Hypochlorous acid partially breaks down into the hypochlorite anion (OCl?) and
hydrogen cation (H+). Hypochlorous acid is a strong oxidant, so the remaining hypochlorous acid in the solution oxidizes the hypochlorite anion
producing the irritating and toxic chlorine gas (Cl2). |
ClO- + HClO + H+ ⇌ Cl2 + ?
That doesn't even make sense. I get that these articles are written for beginners and those just getting into chemistry, but come on. Keeping it
simple by calling protons H+ instead of H3O+ is one thing, but this is just wrong. What most likely happens is the formation of a
hypochloronium ion, followed by nucleophilic substitution by an aqueous choride ion to give water and Cl2 (as mentioned above).
ClO- + H+ ⇌ HClO
HClO + H+ ⇌ H2OCl+
H2OCl+ + Cl- ⇌ Cl2 + H2O
[Edited on 2-19-2015 by Darkstar]
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Molecular Manipulations
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I doubt it, but it might give you metal fume fever!
But really, do you not have hydrochloric acid?
-The manipulator
We are all here on earth to help others; what on earth the others are here for I don't know. -W. H. Auden
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Metacelsus
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If you have sulfuric acid, you can easily make it from salt.
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Cou
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Sorry, I'm a chemophobe... just because someone is chemophobic doesn't mean they can't be an amateur chemist :p
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Texium
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| Quote: Originally posted by Cou |
Sorry, I'm a chemophobe... just because someone is chemophobic doesn't mean they can't be an amateur chemist :p |
Umm, sorry, but it kind of does mean that... if you use reasonable safety procedures whenever necessary and know what you're doing,
you have nothing to worry about. You can't go very far when you limit yourself so much.
I've observed that you often tend to post rather distressed and dramatic posts regarding both lab safety and legal issues in multiple threads. Chill out dude. You get overly worked up about this stuff. Respect chemistry, but do not fear it.
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AJKOER
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An interesting paper: "Effect of chloride ion on the kinetics and mechanism of the reaction between chlorite ion and hypochlorous acid." Available
from: http://www.researchgate.net/publication/23141635_Effect_of_c... . On page 6, to quote:
"The most interesting steps are the chloride-catalyzed ones (kr1 and kr6). Both are appearing when HOCl is one of the reactant. For the interpretation
of the chloride catalysis, we should start from the plausible assumption of Eigen and Kustin, that the hydrolysis of chlorine in fact is a two-step
process, namely:
Cl2 + H2O = Cl2OH- + H+ (R8)
Cl2OH- = HOCl + Cl- (R9)
.... Assuming Cl2OH-to be the reacting species, the third-order V′1 = k′1 [HClO2][HOCl][Cl-] equation can be replaced by V′1=
k′1KR9eq[HClO2][Cl2OH-]. Similar transformation applies for kr6. It seems to be a reasonable assumption that these equilibria and the increased
reactivity of Cl2OH-are responsible for the appearance of chloride catalysis in this and in many other redox reactions of the oxychlorine species. As
chloride ion is one of the product of the reaction, it is in fact an autocatalyst. The difference between the rate of the uncatalyzed and
autocatalyzed path is not very high, thus the typical autocatalytic feature of the product formation does not appear on the experimental curves. "
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