UPSC Combined Geo-Scientist, Mains · 2017 · Mains Paper I

Q1(i). Average and individual oxidation states

Question

Find the oxidation states of (i) Br in Br₃O₈, and (ii) C in C₃O₂.

The average oxidation states are +16/3 for Br and +4/3 for C; individual atoms need not have these fractional values.

For Br₃O₈, let the average Br oxidation state be x.
Carbon suboxide has the structure O=C=C=C=O.
Thus the sum for carbon is 2+0+2=4 and its average is 4/3. A fractional average is not a fractional charge on every atom.

The full model answer

As written for the answer booklet: the diagram carries the working, the lines stay short. Read here only; it is not offered as a download.

CoversAverageindividual oxidation statesOxidation numbers