a.dunn.wa
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Redox reaction with Sulfuric acid and hydrogen iodide
Hi All,
Hope someone could help me out here.
We mixed sulfuric acid (H2SO4) with hydrogen iodide (HI) and we have down that this is the chem RXN:
--> SO2 (aq) + I2 (g) + 2 H2O (l)
The problem where we aren't sure of is what reduces the sulfur, and what oxidized the iodine.
Is this a special case where the sulfuric acid acts as both the reducing and oxidizing agent, or what is going on here?
Thanks in advance,
Andy
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barley81
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Sulfuric acid is the oxidizing agent, and hydriodic acid is the reducing agent.
Sulfuric acid has sulfur in the +6 oxidation state. Sulfur dioxide has sulfur in the +4 oxidation state. Sulfur is reduced in the reaction.
HI has iodine in the -1 oxidation state. Elemental iodine has oxidation state 0. Iodine is oxidized in the reaction.
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AJKOER
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The reaction is multi-step. One could also write with the formation of dilute H2SO4 the reaction as:
Net: SO2 + H2O + [I2 + H2O] --> 2 HI + H2SO4
and note that:
I2 + H2O <--> HOI + HI
HOI --> 2/3 HI + 1/3 HIO3
1/3 HIO3 + H2SO3 --> 1/3 HI + H2SO4
so, in my opinion, the answer of what is oxidized and reduced, and undergoes both (REDOX), should be specific to the individual equations above. As
each of the equations and equilibriums are actually impacted by such factors as pH, temperature and concentration issues, the net reaction may or may
not proceed so the net reaction, in this case, is an interesting (but questionable I would think) summary tool, and only someone lacking understanding
of the underlying chemistry would turn it into the question your proposed.
My retort is not so much aimed at demeaning your teacher/test preparer as to point out that sciencetists should teach science, and not a professional
teacher with some science. In my personal experience in a great suburban school in America, I have a very dedicated Chem teacher who was also a coach
(sports). He have apparently been giving bad answers to regent tests (the official multiple choice answer was, in fact, wrong for years). I, however,
a 16 year Chem geek, pointed out the fact that I thought the answer was wrong and explained why. The teacher agreed and I became the resident Chem
expert (not my teacher). This story is true, and I would state, a sad commentary.
[Edited on 31-8-2012 by AJKOER]
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elementcollector1
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Ha... I've had similar experiences.
So AJKOER, where did the H2SO3 come from?
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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