Can you have reduction without oxidation

If an electrode reaction has dissolved oxygen as a reactant, is the electrode and anode or a cathode? What balanced equation represents a redox reaction? How are redox reactions involved in electrolysis? Why are oxidation reduction reactions coupled? What do oxidation reduction reactions involve? In each of these bonds, you have a pair of electrons that are being shared by both the hydrogen and the oxygen.

But we also know that this isn't a completely equal sharing of the electrons. We look on the periodic table here, oxygen is far more electronegative than hydrogen is.

And so because of that, the electrons in these two bonds are going to spend more time around oxygen than they are going to spend around the hydrogens. And we've seen this before. This would give the oxygen end of the water molecule a partially negative charge.

That's the lowercase Greek letter delta. We use that for the notation of partially negative. And on the hydrogen ends of the molecule, we're going to have a partially positive charge. Now, this is the reality. But as we'll see later on in future videos, it's sometimes inconvenient to have this partial messiness.

And so what I'm going to do right now is introduce you to what is fundamentally just an intellectual tool.

It's just a convention that chemists have invented that allow us to get our heads around a lot of reactions and allow us to think about how is a reaction likely to occur. And that intellectual tool is the idea of oxidation states. What the oxidation state is, even if you're in a situation where you have covalent bond, you say, well, look, I understand.

Those are partial charges. These are covalent bonds. The electrons are being shared. But I don't like this partial stuff. I want to just assume hypothetically, what if these were ionic bonds?

And you say, well, if these had to be ionic bonds, then the oxygen would nab the electrons from these pairs. And so the oxygen would have a fully negative charge, a negative 2 charge. And the hydrogens would have a fully positive charge each.

And so, if we were to write down the oxidation states for the atoms in the water molecule-- let's write that down, so H2O-- we would say that oxygen has an oxidation state of negative 2, and each hydrogen atom has an oxidation state of plus 1.

And notice, the whole molecule is neutral, and these things cancel out with each other. Positive 1, positive 1, that gets you to positive 2. Then you have negative 2. They cancel out. Now, the one thing, I keep saying this is negative 2, but I wrote the negative after it. If I wanted to write positive 1 as an oxidation state, I would actually write it as 1 positive, although you can assume that if someone just writes the positive.

And this is just the convention, to write the sign after the number when we are writing actually ionic charges or oxidation states, because an oxidation state is nothing but a hypothetical ionic charge. If you really had to-- if you were forced to assume these aren't covalent bonds, but these are ionic bonds. Once again, I want to stress.

This is the reality. Therefore, magnesium is a reducing agent. Another way of putting this is that the copper II ion is removing electrons from the magnesium to create a magnesium ion. The copper II ion is acting as an oxidizing agent.

Confusion can result from trying to learn both the definitions of oxidation and reduction in terms of electron transfer and the definitions of oxidizing and reducing agents in the same terms.

The following thought pattern can be helpful:. Jim Clark Chemguide. Oxidation and reduction in terms of oxygen transfer The terms oxidation and reduction can be defined in terms of the adding or removing oxygen to a compound. Oxidation and Reduction with respect to Oxygen Transfer Oxidation is the gain of oxygen. Reduction is the loss of oxygen. Oxidation and reduction in terms of hydrogen transfer These are old definitions which are no longer used, except occasionally in organic chemistry.

Oxidation and Reduction with respect to Hydrogen Transfer Oxidation is the loss of hydrogen. Silver I cation accepted the electrons from iron, oxidizing it. If an electode reaction has dssolved oxygen as a reactant, is the electrode an anode or a cathode? If an electrode reaction has dissolved oxygen as a reactant, is the electrode and anode or a cathode? What balanced equation represents a redox reaction? How are redox reactions involved in electrolysis?

Why are oxidation reduction reactions coupled? What do oxidation reduction reactions involve?