Sure! Let's find the oxidation number of each element you mentioned:
A. To find the oxidation number of nitrogen in N2H4, we need to know that the overall charge of the molecule is zero. Since hydrogen is typically assigned an oxidation number of +1 and there are four hydrogens in N2H4, their total contribution would be +4. Therefore, the oxidation number of nitrogen can be calculated as follows:
2(N) + 4(H) = 0
2(N) + 4(+1) = 0
2(N) + 4 = 0
2(N) = -4
(N) = -2
So, the oxidation number of nitrogen in N2H4 is -2.
B. To find the oxidation number of iron in Fe2+, we know that the overall charge of the ion is +2. Therefore, the oxidation number of iron is +2.