Question

oxidation number for oxygen in O2F2 and H2O2.

Answer 1

the oxidation number of oxygen h2o2 is -1
hydrogen peroxide has the ability to gather two or more electrons for h2 ion.so the oxidation number of oxygen becomes -2. it also act as a  reducing agent. so inturn oxidation number of oxygen becomes 0.
 oxidation number of o2f2 is -1. A fluoride ion would gain an electron to a -1 charge, so each has an oxidation number of -1.

Answer 2

O2F2 = 2(x) + 2(-1) = 0
2x - 2 = 0
x = +1

H2O2 = 2(1) + 2(x) = 0
2 + 2x = 0
2x = -2
x = -1