Question

How to determine if a reaction is a redox reaction?

I need to know how...
I've got a test about it tomorrow..
Also how to determine which is oxidized and reduced?

Please help me.Thanks.

Answer 1

If there is change in oxidation state of a compound then there is a redox reaction. If a compoun's oxidation number has increased then it is getting oxidized, if its oxidation number has decreased it has been reduced.

Answer 2

Do you know how to calculate oxidation number?

Answer 3

no

Answer 4

Rules for deciding oxidation number.
Anything in elemental state is 0 (eg., Cu or Na or O2)
All alkali metals(Na,K,Li,Rb) in any compunds are +1. eg, NaCl.
Oxygen is always -2.(except O2 and O3).
Hydrogen is always +1.
All other elements areobtained by balancing oxidation number and charge

Answer 5

ok.
how do i know which is oxidized and which is reduced?

Answer 6

Lets do some xamples CuSO4 + Zn-> ZnSO4+ Cu.
Can you tell me all oxidation number of all compounds.

Answer 7

I'll do this one for you,
Reactants, In first compound, SO4 is 2- charge since CuSO4 is neutral so oxidation number of Cu in CuSO4 is 2+. Now Zn is in elemental state hence it would be 0.
Products, In ZnSO4 again Zn is Zn2+ and Cu is 0.
Did you understand till here?

Answer 8

yep, i got it there

Answer 9

Fine So now in reactants side if you see Cu is 2+ but in products it is 0. This implies there is a redox reaction.
Now whichever elemnts oxidation number is increasing it gets oxidized whichever oxidation number is getting decreased it is gettting reduced.
So here Cu becomes from 2+ to 0 that means it got reduced while Zn went from 0 to 2+ which means it got oxidized.

Answer 10

wow, thanks.. i got it already
Just one more question,
how do you determine the reducing agent and the oxidizing agent?

Answer 11

Whatever gets oxidized is the reducing agent.
Whatever gets reduced is oxidizing agent.

Answer 12

Here Zn is the reducing agent as it got oxidized.

Answer 13

ok, thanks :))

Answer 14

No problem.