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    Potassium manganate (VII) reacted with an unknown substance, turns from purple to form a brown precipitate.

    What functional group does this suggest the presence of?
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    (Original post by Geek1337)
    Potassium manganate (VII) reacted with an unknown substance, turns from purple to form a brown precipitate.

    What functional group does this suggest the presence of?
    Alcohol(primary and secondary, not tertiary), alkene

    http://www.chemguide.co.uk/organicpr...nes/kmno4.html
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    (Original post by shengoc)
    Alcohol(primary and secondary, not tertiary), alkene

    http://www.chemguide.co.uk/organicpr...nes/kmno4.html
    Can it also turn colourless as well?
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    (Original post by xxxpenguinnnxxx)
    Can it also turn colourless as well?
    yes, typically it is purple to colourless/pink, which is aqua-coordinated Mn(aqueous solution). The brown colour(ppt) might arise if there is no acid used in your test, ie the Mn(VII) is reduced to Mn(IV), the ppt being MnO2(oxidised in air).

    However, with acid added, you can see from combining half eqns(very common in titration), you get an overall favourable reduction of Mn(VII) to Mn(II).

    Have a read on

    http://www.chemguide.co.uk/inorganic...manganese.html
 
 
 
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