colour change in the reaction between C2O42- and MnO4-

2003

2007-08-23 1:38 am

The reaction between ethanedioic acid solution and acidified potassium manganate (VII) solution
.5H2C2O4 + 2MnO4- + 6H+ --> 2Mn2+ + 10CO2 + 8H2O
is it necessary to add any indicator to this titration? Explain.

ans: MnO4- = indicator.The colour change of the reaction mixture at the end point should colourless to pink (as the presenece of an excess MnO4)

why colour change 係colourless to pink?
MnO4- is not purple colour咩,Mn2+is not colourless?

回答 (1)

pha

2007-08-24 4:41 am

✔ 最佳答案

It is obvious that titrating ethanedioic acid solution with acidified potassium permanganate, means that putting acidified KMnO4 in the burette.

When you drop the acidififed KMnO4 to the conical flask, the purple colour of the titrate will become very pale pink in the flask as it is reduced to Mn 2+. You should know about it.

So, the endpoint is that, there would be a slight amount of KMnO4 being unreacted since all the ethandioic acid used up. The colour change would be pale purple. Then you stop it.

The model answer may be wrong.

參考: ME

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