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M Hess

Why is sulfuric acid a strong oxidizing agent?

Andy Fletcher  Follow

In sulphuric acid ( H2SO4), the oxidation state of sulphur is +6 and it can go to lower oxidation states but not to the higher oxidation states. Therefore, H2SO4 acts only as an oxidizing agent but not as a reducing agent.

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Bob Collier  Follow

It act as acid when some base is present. Since sulfuric acid is strong acid, it will react with weak amphoteric base water and gives H3O+ ions in dilute solutions. But in conc solution no water or little water is present so it proceeds in the direction to form water. (Since it has great affinity to act as acid). If anyhow it gets converted to form H2SO3 (sulphurous acid) which is not stable compound. It will dissociates into SO3 + H2O, thus will fulfill its desire. So sulphuric acid in concentrated forms gives nacent oxygen and forms sulphurous acid. This nacent oxygen act as oxidizing agent.

H2SO4 (conc) ==> [O] + H2SO3

H2SO3 ==> SO2 + H2O


H2SO4 (conc) ===> [O] + SO2 + H2O

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Andy Hill  Follow

Sulfuric acid is a strong diacid … and the GIVEN equilibrium lies to the RIGHT as we face the page…

[math]H_{2}SO_{4}(aq) + 2H_{2}O(l) ightleftharpoons 2H_{3}O^{+} + SO_{4}^{2-}[/math]

Now here we got a formal [math]S(VI+)[/math] oxidation state … and this is generally RETAINED, with the result that sulfuric acid is a STRONG, but non-oxidizing acid…and of course there are many sulfate salts…

Sulfurous acid, [math]H_{2}SO_{3}[/math], i.e. [math]S(+IV)[/math], is a less strong acid…

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Alan Siegel  Follow

A reducing agent contributes electrons. It is a strong acid so the two H+ ions have no electrons to contribute. It has 4 oxygen atoms combined with a weak oxidizing agent (sulphur). They are attracted to more electrons than the two they already have (SO4)2-. Fluorine might be a strong enough oxidizing agent to take electrons from this molecule, but nothing else I can think of.

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Charles McDevitt  Follow

Sulfuric acid only oxidizes in the concentrated form. Oxidizing agents are good at removing electrons by accepting them or transferring them to another atom or molecule. In the case of sulfuric acid, it accepts electrons. It is a good oxidizing agent because of its positively charged sulfate ions SO4- that bind positively charged electrons. Sulfuric acid is not as strong an oxidizing agent as elemental fluorine, nitric acid, or potassium permanganate. These three molecules have a greater affinity for electrons than sulfuric acid.

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Dave Belyea  Follow

There are lots of chemical reactions in which sulphuric acid acts as an acid and not as an oxidizing agent, so the “always" in the question is wrong…

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