sulfuric acid from sulfur flour

[woo-jong]

I wonder whether my theory is correct or not

My theory :

S+O2 --------> SO2

when sulfur burns(reacts with oxygen), sulfur dioxide is formed

and this gas dissolves in water and makes sulfurous acid

SO2+H2O ------> H2SO3

sulfurous acid is decomposed by electrolysis

H2SO3 ---electrolysis---> H2↑+SO3

sulfur trioxide makes sulfuric acid with water.

SO3+H2O ------> H2SO4

is my theory correct? if there is some mistake, please tell me about my mistake. and I maybe have some mistake in my English ,too because I'm Korean person

<small>[ June 07, 2002, 01:59 PM: Message edited by: ALENGOSVIG1 ]</small>

[imported_reodor_felgen]

I don't think electolyse of sulfurous acid would yield sulfuric acid.

you could try to burn sulfur and then convert the SO2 created too SO3 via an catalyst like iron oxide or platinum. you should apply strong heat too the catalyst and then lead the SO3 into water.

[ALENGOSVIG1]

I think this may have been discussed before but im not sure. This thread is in the wrong section and you double posted. <img border="0" title="" alt="[Eek!]" src="eek.gif" />

Either figure out how we operate around here or you'll get banned. :mad:

Im hoping something good will come out f this thread so im not going to close it.

Moving to chemistry related.

<small>[ June 07, 2002, 02:07 PM: Message edited by: ALENGOSVIG1 ]</small>

[rikkitikkitavi]

first, a SO2 solution in water doesnet form H2SO3, but it rather behaves if there was an acid
with that composition.

H2O+ SO2 = H2SO3 forms an equlibrium which is strongly shifted to the left.

For most practial uses it doesnt matter.
(solubility of SO2 @0C about 2,2 moles of SO2 / liter)

a little electrochemistry :

1)H2SO3 + H2O = SO4 + 4H+ + 2 e- emf = -0.172

2)2 H2O = O2 + 4 e- + 4 h+ emf= -1.229

3)2H2O + 2 e- = H2 + 2 OH- emf= -0.8229

add rxn 2*3) and 2)

4H2O + 4 e- + 2H2O = O2 + 4 e- + 4 H+ + 2H2 + 4 OH-

(h+ and OH- immedieately recombines into water )

2H2O =&gt; 2H2 + O2 emf = -1,229+ (-0,8229) = -2,06 V normal water electrolysis

add rxn 1) + 2)

H2SO3 + H2O + 2H2O + 2e- = SO4-- + 4H+ + 2e- + H2 + 2OH-

H2SO3 + H2O = SO4-- + 2 H+ + H2
emf = -0,172 + (-0,8229) = -0,9949 V

last reaction takes less energy and is favoured over ordinary waterdecompostion.
In theroy it should work. The low potential of H2SO3 =&gt; H2SO4 show that it is a powerful reducing agent and has found much use as such to.

The reason why it aint used ?
Probably because normal H2SO4 production produces acid
that sells for about 30 US$ per metric ton in large shippments...
and the fact that solubility of SO2 in water isnt that great, which limits the concentration of H2SO4 produced, which calls for very expensive distillation of it..

electrolysis is always expensive, especially with this corrosive environment

but in theory , it should work

/rickard

[A_W]

rik., SO2+H2O DOES form H2SO3, but as you stated, the equlibrium is strongly shifted to the left. Therefore, only a few percentages of the SO2 reacts to form H2SO3. The rest will remain as a SO2 solution in the water.

However, it seems that you're much more into chemistry than I am, so I'm just saying what's in my encyclopedia. My encyclopedia also says that H2SO3 very easily converts into H2SO4 by picking up an oxygen atom. I was therefore thinking of, maybe an oxider to react the H2SO3 into H2SO4? Just a theory. :)

When SO2 is released into the atmosphere (when burning petroleum etc.), it oxidizes to SO3, wich reacts with water in the air, forming H2SO4 (--&gt; acid rain!). It wouldn't be that difficult to convert SO2 into SO3 in the lab, would it???

[VX]

I'm sure that I can remember reading that NO2 catalises the reaction, in the case of forming SO3 in the Atmosphere.

It was a two stage reaction, something like this, not sure if this is the reaction though. :rolleyes:

SO2 + NO2-----&gt; SO3 + NO

2NO + O2------&gt; 2NO2

[kingspaz]

hmmm......i thought the acid rain was caused by the formation of H2SO3....
but that it seems more likely to be what VX has said now i've found out more about H2SO3.
rickard, thanks for that post.

[Microtek]

There is a web-page called "From Caveman to Chemist" that deals with assorted primitive chemistry. One of the experiments is about making sulfuric acid by heating sulfur with KNO3 and leading the gaseous products over water. Lots of NO2 is produced, which he says takes part in the process.

[A_W]

Sounds interesting (but dangerous). I doubt that ALL of the NO2 would take part of the reaction. Some of the NO2 would dissolve into the water, hence you would get a mixture of diluted H2SO4 and HNO3, am I right? Therefore, one should have a way of separating the two acids.

[zaibatsu]

<a href="http://cator.hsc.edu/~kmd/caveman/" target="_blank">http://cator.hsc.edu/~kmd/caveman/</a>

[rikkitikkitavi]

NO2 oxidizes SO2 to SO2 when water is present, this was used as a industrial process (lead-chamber process) to make sulfuric acid until the contact-process (with V2O5 catalyst) took over.

This has been thouroghly discussed in a previous thread, aswell as other methods of making H2SO4.

Other oxidants that work in the water-phase is f e x H2O2 and Cl2.

( H2O2(l) + SO2(g) =&gt; 2 H+ + SO4-- )

H2O
( Cl2(g) + SO2(g) =&gt; HCl (aq) + H2SO4 (aq) )

I read about the later process in a book that it has been used as an industrial process: Cl2 and SO2 gas where feed to absorbtion towers with water, and the gases reacted in the aqeous phase, but nowadays it is much to expensive process, because Cl2 is produced with electrolysis (NaCL =&gt; Cl2 + NaOH ).

Nothing can compete with the contact process, actually sulfuric acid is one of the cheapest chemicals available, because the raw material is cheap and the process puts out large amount of energy , which can be used for heating or generating electricity. A sulfuric acid plant of 400000 tpa generates about 40-50 MW surplus energy . Just a bit completetly unneccesary information.. :)

/rickard