Balancing redox equations

Question

reactants: Cu, NO3^- (the negative sign is nex to the O, above the 3).
products: Cu^2+, NO2

Medium: Acidic

Cu+ NO3^- ----> Cu^2+ + NO2

Okay, I don't understand how to do this problem...but something someone needs to clear up for me...why does N in NO3^- have an oxidation state of 5 and in then NO2 has an oxidation state of 4?

Answer 1

IT has a lower oxidation state because it was oxidized. Nitrogen can have several states.

Cu+NO3- + 2H+ >> Cu-2 + NO2 + H20

acidic medium means Hydrogen ion is present.

Answer 2

so, b/c it is acidic, there is always an 2H and H2O even before I balance it?