plz explain me TITRATION IN REDOX REACTIONS. i have not done any practical related to it, thats why i m facing problem in it.plz tell what is the set up and what process is process going on.i really cannot understand its explanation in NCERT or any site on web.i hope u will be a help to me.with regards,SAUMYA

Dear student,

Key Concepts

• A REDOX titration is a volumetric method that relies on the oxidationof the analyte (substance to be analysed).
• The titrant (solution of known concentration) is often an oxidising agent.

  Common oxidising agents are:

  1. permanganate ion (MnO₄^-)
     MnO₄^-_(aq) + 8H⁺ + 5e -----> Mn²⁺_(aq) + 4H₂O     E^o = +1.51V
     purple permanganate ion (MnO₄^-) is reduced to colourless manganese (II) ion (Mn²⁺)
  2. dichromate ion (Cr₂O₇^2-)
     Cr₂O₇^2-_(aq) + 14H⁺ + 6e -----> 2Cr³⁺_(aq) + 7H₂O     E^o = +1.23V
     orange dichromate ion (Cr₂O₇^2-) is reduced to green chromium (III) ions (Cr³⁺)
• At the equivalence point E_(forward) = E_(reverse), or, E_(cell) = 0
• If the REDOX reaction does not produce a well-defined colour change at the equivalence point, an indicator should be used in the titration.
  Starch can be used as an indicator for REDOX titrations using iodine as the titrant (iodine is a weak oxidising agent) because starch forms a blue complex with iodine.
• The REDOX titration curve is a plot of Electrode Potential (volts) vs volume of titrant or analyte.

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