I don't get redox reactions....?

Question

I don't understand red ox. I mean... all the numbers are supposed to balance and okay, fine, but what do they all mean? how do the molecules have charges and then change charges? and they're not even charges, they're "hypothetical" charges. so what does that mean? it's a potential to be charged +2 and they lose that potential in the reaction? and how does it all tie into reactions in general? do all reactions involve redox? and if we just balance any equation, like we were doing before we learned redox, was that all wrong because we didn't take into consideration the "hypothetical" charges? I'm sooo confused. :(

Answer 1

It's not hypothetical - it really happens

look at this simply reaction:

Fe + CuSO4 --> Cu + FeSO4

1/2 cells

Fe --> Fe+2 + 2e-

Cu+2 + 2e- --> Cu

You add Iron metal to the one side of the reaction, and you get solid copper metal out of the other side - it is NOT "just on paper" - it REALLY happens.

If we like we can use a potentiometer to measure current flow in a cell that is set up according to this reaction. Electrons DO change hands.

Answer 2

Hi Daisy. Sorry to hear that you get confuse. I believe if you invest more time on understanding the principle it is not that confusing. Let me help you.

Let me start by stating that there are soooo many reaction that involves reduction-oxidation (redox). those that do not are the so called metathesis reaction ( AB + CD --> AD + BC), this includes the acid-base reaction and the other reaction that does not follow redox is precipitation reaction. So as you can see understanding redox reaction is a major part of understanding chemical reaction.

Do we need to break down all the charges in a redox. A simple answer would be "no" since after all you don't see the electron directly. I notice that there is suggestion that you could measure the electron as electric current..this is however not always the case and is not a prerequisite of a redox reaction.
So why do one need to write all the charges involves in a redox reaction. The answer is simple: when you later wanted to get deep in chemistry you'll have to be able to understand a reaction (yes including lots of complex redox reactions) and when it happens there is no shortcuts other than knowing how and where to the electron are being transferred.
so what are the charges anyway? first of all the charges of an element or molecule is real and that's you have the so called ions, which is basically normal atoms or molecule with charge on it.

and what is oxidation number is it really necessary? Hmm i notice that there is one particular answer that suggest oxidation number don't have any physical or chemical meaning. That is unfortunately false. Oxidation number is as real as charges. It just a different angle of viewing charges.
officially oxidation number is the total charge of a molecule or an atom if there were no groups, other atoms, ligands attached to that particular atom or molecule, in another word the total charge of an element/molecule if there were no electron being shared with that element/molecule. confusing?
let me put an analogy to it lets say you have a room with 8 chair in it and there are 5 people standing outside the room and 3 people are sitting inside. the empty chairs will represent oxidation number (oxidation state) of the room, peoples will represent electrons involved in the process and people sitting on the chair simply means that there are electrons being shared. At the current condition we will say that the oxidation number of the room is +5 because there is still a capacity of sharing 5 more electron (people), had there were no people sitting in the room the room will have the maximum capacity hence the highest oxidation state of the room is +8 (it is similar to Mn that has oxidation state of 2,4,6 and maximum 7). so far clear.
Now let's say 2 people come into the room and sit, so there are PROCESS/REACTION of people moving into the room (electron are being moved into the room, the room are reduced the process called REDUCTION while the space outside the room loss its two people therefore the space outside the room is oxidised since it looses 2 electrons/people) so what happen next is that the room is now more crowded and less empty chair are available, the room now have an oxidation number of 5-2 = +3 and the involve electron is -2e. If you only take a snapshot of the room and the space outside after and before the process you don't really see what happened (no electron transfer were observed) but suppose you want to investigate the process and you took a rolling camera, then you are able to say at a point the space outside the room loose two electron and at the next step the room receives the electrons and change the oxidation state of the room. It is that simple!

let me just sum it up:
1. the redox is always coupled reactions. When the room was being filled (reduced) of course the other part, that is the space outside, will be emptier (oxidised)
2. both charges and oxidation number (oxidation state) are real, they are not by any means for bookkeeping purposes, they are strongly related but different in perspective
3. you don't have to write every electron involve in every reaction (I don't do it everytime myself) but when the time comes that you have to have more insight of the reaction then you should be able to do that, so simply take this time as a practice.

I hope I've helped you a little with understanding the redox. don't panic chemistry is not as complicated as you might thing. it is fun =)

Answer 3

You are right to be confused. The first problem is oxidation numbers. Oxidation numbers have no physical or chemical meaning. They are an arbitrary bookkeeping system to help you balance equations. So you must learn how to calculate oxidation numbers of elements on both sides of the equation. After that, you have to balance the number of electrons (-1e) ganed with the electrons lost. Once you balance the electrons, the other numbers will begin to fall out.

All reactions are not redox reactions. The way you will know is to ask, "Hey! Did something just change oxidation number here?"