[Reyah]

Hey all!

This task has me puzzled:

Determine which of these chemical reactions that are redox reactions:
a) Na+ + Cl- -> NaCl
b) Cu2+ + Fe -> Cu + Fe2+
c) 2Na + 2H2O -> 2Na+ + H2 + 2OH-

I answered that A and C were redox reactions, but according to the book B & C are. Why is this?
I thought that redox reactions were classified by having both a reduction and an oxidization?, and as far as I can see B has two reductions...?

Anyways, any and all help is greatly appreciated!

[cpncoop]

A redox reaction is a reaction that changes the oxidation state of one or more molecules during the course of the reaction.  In A, Na + + Cl - --> NaCl, there is no change is oxidation states from one side of the reaction to the other, Na is still +1, Cl is still -1 for the equation to be balanced.  In B, you go from Cu 2+ to Cu (O) and Fe (0) to Fe 2+, so the oxidation states change, and it is a redox reaction.  Using this same approach, you should be able to figure out why C is also a redox reaction.  But if you have trouble seeing why, please let me know.

[Reyah]

Thank you so much. I clearly see where I made my mistakes thanks to your explanation.

[Borek]

A redox reaction is a reaction that changes the oxidation state of one or more molecules during the course of the reaction.

Please explain what is oxidation state of molecule.

Can you give example of a redox reaction where oxidation state of only one molecule changes?

[cpncoop]

I apologize for my sloppy response.  Atoms have oxidation states, not molecules.  And as you point out, if one atom changes its oxidation state, another in the reaction must also change in an equal and opposite amount to maintain charge neutrality.... While I made some grammatical errors in my response, I think it helped the person solve the problem, and find your response a bit patronizing.