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It's hard to pinpoint what the problem here is since I don't have the mentioned book to compare an answer with. The simplest way is write down half-reactions for reduction (red) and oxidation (ox) processes once you've assigned oxidation numbers (denoted above the symbols of the elements which are participating in a redox reaction), then balance the number ...


Run everything one more cycle and you are totally safe. Copper is highly soluble in water, so it will entirely dissolve and go away, not contaminating your plates.


A balanced equation must have a mass balance i.e., the masses should be equal on both sides and charges must be balanced as well. Oxidation number is just a way of book-keeping. Nothing fundamental there. $$\ce{Fe^2+ + Cr2O7 + 14H+ -> 2 Cr^3+ + Fe^3+ 7 H2O}$$ What are you forgetting? It is mass balanced. Does $\ce{Cr2O7}$ exist? Hint: It is potassium ...


On negative oxidation states, in general Although it's usually a topic that's covered relatively late in a chemistry education, negative oxidation states for transition metals[1] are actually quite alright. On the Wikipedia list of oxidation states, there are quite a number of negative oxidation states. Some textbooks have tables which only show positive ...


If there is an element in the reactants and it is not an element in the products then yes, oxidation or reduction has occurred. Acid-base reactions are pretty much non-redox reactions. But it is always handy to learn the oxidations numbers. Extra sources Do non-redox reactions exist?

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