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REDOX question

markosheehan

Member
Jun 6, 2016
136
By using oxidation numbers can someone show me what is oxidised and reduced

Fe203+3co->2Fe+3co2
 

Klaas van Aarsen

MHB Seeker
Staff member
Mar 5, 2012
9,491
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
Jun 6, 2016
136
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
Mar 5, 2012
9,491
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).