Please help me with this question.
Assign oxidation numbers to each element in this equation, and hence identify the oxidant and reductant
Fe2O3 (s) + 3CO (g) -----> 2Fe (s) + 3CO2 (g)
I get so confused with the whole oxidant/reductant/oxidation/reduction thing. @___@
To assign oxidation numbers, you have to follow some rules, one of them being that a free element such as iron, which is a product in this reaction, has an oxidation number of 0.
Another important rule is that a compound has a net oxidation number of 0-so adding up the oxidation numbers of the individual elements making up the compound. So, Fe203 is a compound and it must have a net oxidation charge of 0. Valence of oxygen is 2 and we know oxygen is electronegative (has an affinity for electrons), so the oxidation number for oxygen is -2 times 3 (because there are 3 oxygen atoms and we are accounting for all of them).
So, this means that the Fe2 component must have a positive charge of +6. This charge is distributed equally between the 2 Fe atoms.
Let's look at CO-oxygen -2, Carbon must have +2 oxidation number.
CO2-oxygen negative 4, so carbon positive 4.
Now that we have assigned our oxidation numbers, our next step is to work out what is the oxidising agent and what is the reducing agent.
Oxidising agent-what oxidises something and itself gets reduced. To be reduced the oxidation number needs to decrease. We see this with Fe203, which is a reactant and leads to the free element Fe. So, this is a oxidising agent/reductant.
CO (carbon monoxide) is the reducing agent because it gets oxidised-the oxidation number on the carbon atom increases.
Increase in oxidation number means-become oxidised and therefore reducing agent. reducing agent reduces Fe2O3 (because you get free iron).
Hope this makes sense,
Good luck.