[Hentrox]

Question c. (shown in photo 1). Book states that answer is " Cu oxidised (0  +2), N reduced (+5  +4)"

As can be seen from my working on it in photo 2, I have also come to this conclusion, however, it also appears that H has gone from an oxidation state of +1  +2, and that O has gone from an oxidation state of -6  -4 (i.e. they've both been oxidised). Why am I wrong? I have followed everything the teacher has said to do...

And then in question d. it gets even more mind f**king. You can see my assigning of oxidation states/numbers to the elements in the bottom of photo 2. I get that Pb has gone from +4 to +2 and that Cl has gone from -1 to 0 (in one situation...). Cl HAS ALSO gone from -1 to -2??? WHAT??? On top of that, like in the previous question, H has gone from +1 to +2. I am losing my mind.

[Hunter2]

Hydrogen and oxygen dont change its oxidation numbers in these reactions.

[Corribus]

@Hentrox, you seem to be forgetting that some of those compounds have multiple oxygen atoms. The oxidation state of oxygen in nitric acid is not -6. It is -2 per oxygen atom. And in nitrogen dioxide the oxygen state of oxygen is still -2 per oxygen atom. But there are only two oxygen atoms in nitrogen oxide, so the overall contribution of charge from oxygen atoms in this compound is -4. This does not mean that oxygen has changed oxidation states. Oxygen atoms have a -2 oxidation state in both compounds.

[Hentrox]

Thanks so much for the answers guys! Helped tremendously!