SO2 AS REDUCING AGENT



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    ANS-ALKALINE MEDIA

    PLSS PROVIDE A LOGICAL EXPLANATION

    SO2 IN AQEOUS FORMS *H2SO3**NA NOTT H2SO4 NA???

    THEN PLS EXPLAIN



  • @ABCDMA-ABCDMA SO2 is more powerful reducing agent in alkaline medium than in acid medium.
    This is because in acidic medium, it forms sulphuric acid which acts as strong oxidizing agent.

    SO2 acts as a reducing agent because of the liberation of nescent hydrogen in the presence of moisture; SO2 + 2H2O ---------- H2SO4 +2H Alkali neutralises the acid (H2SO4) and shifts the equilibrium in the forward direction producing more nascent hydrogen.however,in acidic medium,the equilibrium is suppressed resulting in a lesser amount of nascant hydrogen.consequently,SO2 is better reducing agent in alkaline medium than in the acidic medium



  • @jai-d-gr8

    I understand the explanation if u come sider so2 forms h2so4 in water...

    But that is wrong. My doubt is So2 forms H2so3 and not h2so4 hence this exp is wrong pls explain after so2 forms h2so3



  • @ABCDMA-ABCDMA When sulfur dioxide is dissolved in water, an acidic solution results. This has long been loosely called a sulfurous acid, H2SO3, solution. However, pure anhydrous sulfurous acid has never been isolated or detected, and an aqueous solution of SO2 contains little, if any, H2SO3. Studies of these solutions indicate that the predominant species are hydrated SO2 molecules, SO2 · nH2O. The ions present in these solutions are dependent on concentration, temperature, and pH and include H3O+, HSO3−, S2O52−, and perhaps SO32−. However, “sulfurous acid” has two acid dissociation constants. It acts as a moderately strong acid with an apparent ionization of about 25 percent in the first stage and much less in the second stage. These ionizations produce two series of salts—sulfites, containing SO32−, and hydrogen sulfites, containing HSO3−. Only with large cations, such as Rb+ (rubidium) or Cs+ (cesium), have solid HSO3− salts been isolated. Attempts to isolate these salts with smaller cations tend to yield disulfites as a product of dehydration.
    2HSO3− ⇌ S2O52− + H2O

    With the exception of the alkali metal sulfites, these salts are relatively insoluble. The HSO3− ion has an interesting structure in that the hydrogen atom is bonded to the sulfur atom and not to the oxygen atom, as might be expected. There is some suggestion that in solution both the sulfur-hydrogen and oxygen-hydrogen structures may exist in equilibrium with one another, but there is no concrete evidence for this phenomenon. Heating solid hydrogen sulfite salts (shown by the equation above) or passing gaseous sulfur dioxide into their aqueous solutions produces disulfites.
    HSO3−(aq) + SO2 → HS2O5−(aq)
    Disulfite ions possess a sulfur-sulfur bond and are therefore unsymmetrical. Addition of acid to the solution of HS2O5− above does not produce “disulfurous acid” (H2S2O5) but instead regenerates HSO3− and SO2. “Sulfurous acid” solutions can be oxidized by strong oxidizing agents, and oxygen in the air slowly oxidizes the solution to the more stable sulfuric acid.
    2H2SO3 + O2 + 4H2O → 4H3O+ + 2SO42−
    Likewise, solutions of sulfites are susceptible to air oxidation to produce solutions of sulfates. Sulfites and hydrogen sulfites are moderately strong reducing agents.
    Sulphurous acid reacts with strong bases to give the corresponding salt which are predominantly reducing in nature
    Ex:H2SO3 + 2 NaOH → Na2SO3 + 2 H2O
    Sodium Thiosulfate is a very strong reducing agent



  • @jai-d-gr8 isnt ur conclusuion the same as H2SO3 is good RA
    thst just means aq so2, how did u show that acidic wont let this happen?



  • @ABCDMA-ABCDMA U haven't understood it clearly .....
    Lemme summarise
    SO2 in water can produce sulphurous as well sulphuric acid....but ur doubt is regarding sulphurous acid if I am correct ...sulphurous acid is moderate reducing agent ...and it's strength can be enhanced only on the addition of a base (alkaline medium )whose reaction I have provided in the previous conversation ...in acidic medium...the dissociation of sulphurous acid reduces due to the existence of a strong acid in the solution ...and hence the reducing nature decreases(common ion effect )


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