Which element is oxidized and which is reduced?

2KCLO3 = 2KCL + 3O2

I wrote that Chlorine is reduced and Potassium is oxidized, however I only got the mark for Chlorine. What has been oxidized then?

1 Answer
Nov 19, 2017

Oxygen was oxidized and chlorine was reduced


Before the reaction, oxygen had -2 oxidation number, but after reaction oxygen lost 2 electrons and it became neutral, so after reaction oxygen has zero oxidation number. It means, that oxygen is reducer and it oxidized.

Note that, potassium before and after reaction had +1 oxidation number, so it is neither a reducer nor an oxidizer