# REDOX question

#### markosheehan

##### Member
By using oxidation numbers can someone show me what is oxidised and reduced

Fe203+3co->2Fe+3co2

#### Klaas van Aarsen

##### MHB Seeker
Staff member
By using oxidation numbers can someone show me what is oxidised and reduced

Fe203+3co->2Fe+3co2
Hi Marko,

Making the ion forms explicit, we have:
$${Fe^{3+}}_2{0^{2-}}_3+3C^{2+}O^{2-}\to 2Fe+3C^{4+}{O^{2-}}_2$$
So $Fe$ gains electrons and as such it is reduced.
And $C$ loses electrons, meaning it is oxidized.

#### markosheehan

##### Member
Hi Marko,

Making the ion forms explicit, we have:
$${Fe^{3+}}_2{0^{2-}}_3+3C^{2+}O^{2-}\to 2Fe+3C^{4+}{O^{2-}}_2$$
So $Fe$ gains electrons and as such it is reduced.
And $C$ loses electrons, meaning it is oxidized.
thanks
I usually go to the periodic table and look at the elements valency and then i take this as the oxidation number. this is not always correct though?
for example carbon has a valency of 4 but in the above equation it is 2+.
so you go off the ones you know like oxygen is always -2 and the oxidation number of a compound must always equal zero.

#### Klaas van Aarsen

##### MHB Seeker
Staff member
thanks
I usually go to the periodic table and look at the elements valency and then i take this as the oxidation number. this is not always correct though?
for example carbon has a valency of 4 but in the above equation it is 2+.
so you go off the ones you know like oxygen is always -2 and the oxidation number of a compound must always equal zero.
Yes, in compounds oxygen is always -2.
The metals (that are oxidized) usually have more than one oxidation number, and the valency doesn't even have to be one of them (copper for example).