Redox and Non-Redox Reactions?

Question

here are some equations im stuck at: are the following reactions redox?

1)2CuCl2(aq) + 4KI(aq) 2CuI(s) + I2(s) + 4KCl(aq)

2)2HNO3(aq) + CuO(s) Cu(NO3)2(aq) + H2O(l)

3)10HNO3(aq) + 4Zn(s) 4Zn(NO3)2(aq) + NH4NO3(aq) + 3H2O(l)

4)2CrCl3(aq) + 3Na2C2O4(aq) Cr2(C2O4)3(aq) + 6NaCl(aq)

Answer 1

Here's a tip, any time you see something in it's elemental form, change from or to a non-elemental form, it's a redox rxn. By definiiton.

So, #1 and #3 are easily redox reactions. (Rxn 1, Iodine, I, changes from KI to elemental I2. Rxn 3, Zn changes from solid Zn to zinc nitrate.)

2 and 4 are a little trickier, you have to assign the oxidation states to compounds. To simplify it a little, you can look at compound ions if they don't change (in rxn 4, the oxalate ion, C2O4 -1, changes partners, but it doesn't change. So don't keep track of C and O, just keep track of the oxidation state of the ion)

Anyway, nothing changes oxidation states in rxns 2 and 4, so they are NOT redox rxns.