How does oxidation state affect color?

1 Answer
Jun 13, 2017

Answer:

There is no necessary relationship.........

Explanation:

There is no necessary relationship.........but generally the metal ions in the higher oxidation states, i.e. #Cr(VI+)# in #Cr_2O_7^(2-)# #Mn(VII+)# in #MnO_4^(-)# tend to be strongly coloured. Since the metal centre is totally oxidized these are charge-transfer bands, which are spin-allowed and intense.

THe redox couple of permanganate to #Mn^(2+)#..........

#MnO_4^(-) + 8H^(+) +5e^(-) rarr Mn^(2+) + 4H_2O#

....is highly useful for redox titrations, in that while #MnO_4^-# is a strong, intense purple...........

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.........its oxidation product #Mn^(2+)# is a high-spin #d^5# system, which is, to all intents and purposes, COLOURLESS in aqueous solution.

For an example of how this might be used in a problem see here.