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From: andrew wilson (andrewwilson550@hotmail.com)
Date: Tue Dec 30 2003 - 19:03:01 EST

  • Next message: Carl Hinote: "RE: [Channel-talkchemistry] Re:Chemistry Question"

    Dear Sir
     
    I need some help please!!!
     
    I need some help on how to tackle the following question on Back Titrations.I have tried to find some information in inorganic texts but have been unable to find a similar example.
     
    Procedure
     
    To 10cm3 of solution A add 25cm3 (xcess) of the EDTA solution and 10cm3 of the NH4OH/NH4Cl buffer solution and titrated the xcess EDTA with 0.01mol cm3 zinc solution using Erichrome Black indicator.
     
    To a second 10cm3 aliquot of solution A added 25cm3 (xcess)EDTA  and 10cm3 of NH4Ac/Acetic acid buffer solution (pH approx 4.5) and next added 50cm3 of alcohol and titrated again with the zinc solution. Dithizone was used as the indicator.
     
     
    I need to be able to
     
    1) Calculate the amount of free (xcess EDTA) present
     
    2) then calculate,by difference, the concentration of magnesium and zinc present in solution A.
     
     
    Any guidance would be greatly appreciated.
     
    Best wishes
     
    Andrew     

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