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Does the reactivity series of metals hold true for organic compounds?

  1. Mar 17, 2014 #1
    I've learnt that a more active metal displaces a less reactive one. So, according to the reactivity series Ca cannot displace Na but in he reaction given at http://en.wikipedia.org/wiki/Soap_scum
    Na is displaced by Ca.
    What is the reason for this exception?
  2. jcsd
  3. Mar 17, 2014 #2
    I am afraid you are wrong. ''Na'' is not replaced by Ca but Na+ is getting replaced by Ca+2. The reason for this displacement reaction is given by Fajan's rule. Fajan's rule states that lesser the size of cation, more stable is the compound/ionic salt. So here, size of calcium cation is lesser than sodium cation and hence greater product stability, thus the product.

    Reactivity series applies to (Metal + Other compound) kind of reactions.

    Eg: Na + H2O = NaOH + 1/2H2
  4. Mar 21, 2014 #3
    But if we have reactions like CuSO4 + Na → Na2SO4 + Cu
    In such reactions we have Cu in the ion form i.e. Cu2+. So in this reaction aren't the cations of copper displaced?
  5. Mar 21, 2014 #4
    Yeah. But, the one displacing it, i.e sodium is in the form of metal.
  6. Mar 21, 2014 #5


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    Staff: Mentor

    This is rather bad example. Better one will be

    2AgNO3 + Cu → Cu(NO3)2 + 2Ag

    or, in the net ionic form

    2Ag+ + Cu → Cu2+ + 2Ag
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