(Original post by Adorable98)
So I have learnt this "phrase"
that I've came up with inorder not to get mixed up with reduced
So here it is:
- Reducing agentis oxidised, it reduces something else - Oxidation.
- Oxidising agent is reduced, it oxidises something else - Reduction.
But at times this "phrase"
doesn't seem to agree in some situations
In my book it says: Cr2+ oxidises
back to Cr3+
and the reaction is called oxidation.
*Shouldn't it be Cr2+ reduces
back to Cr3+
But in this case, the "phrase"
Halogens are reduced
when the gain an electron. As they're reduced
, they oxidise
another substance, so they're oxidising agents.
So my question is "phrase'' correct?
In a redox reaction if one species is oxidised (loses electrons), another must be reduced (gains electrons). Redox reactions are also called, electron transfer reactions, they involve the movement of electrons. In a balanced redox equation the number of electrons gained must be equal to the number of electrons loss. A shorter way to remember this is OILRIG (oxidation is loss, reduction is gain). Lets make it even easier; Cr2+ --> Cr3+ +e-, this has lost an electron, so therefore it's been
oxidised and therefore
the "oxidation state has increased
", see how there's more plusses. Cr3+ +e---> Cr2, this has gained an electron and therefore
the oxidation state has gone down.
When the oxidation number decreases i.e. +3 to +2, reduction has occurred. So in reduction, oxidation state decreases and in oxidation, oxidation state increases (sorry if that was confusing haha XD). Now oxidising agents are electron acceptors (they are what cause another species to lose their electrons, hence oxidising agents), reducing agents are electron donors (they are what cause another species to get reduced). But as we said earlier if something is reduced another must be oxidised. So if a reducing agent is giving away electron, it's losing them it self, so therefore it's being oxidised itself. Finally, let do an example
. CuO + Mg --> MgO + Cu, as this has ionic compounds, lets show their charges (oxidation states), to make it easier to see. [ (Cu2+) + (O2-) ]+ Mg --> [(Mg2+) + (O2-)] + Cu. As you can see copper has been reduced it has gained 2 electrons (cu2+ to cu) and Mg has been oxidised (lost two electrons). Can you see how this is balanced, the number of electrons gained is the number of electrons lost. Now as Magnesium is getting oxidised (it's a reducing agent, it has given away its electrons to copper), and as you can see copper has been reduced so copper has accepted the electrons (it has caused the magnesium to be oxidised as it has accepted its electrons, so it's an oxidising agent). Also the oxygen's oxidation state has remained the same, so it takes no part in the reaction, it's a spectator ion. Let me know if you're still confused
Getting your head around it, can be hard