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Oxidation Reduction Reactions - Redox 26,757 views

Teacher/Instructor Jacqueline Spivey
Jacqueline Spivey

Ph.D.,U.C.Santa Cruz
Teaching at a top-ranked high school in SF

She teaches general and chemistry at a top-ranked high school in San Francisco. Prior to that, she lead and published a number of research studies and lectured at SF State University.

Oxidation-Reduction Reactions, also called redox reactions, are reactions for which the driving force is the transfer of electrons. Oxidation is the loss of electrons and the gaining of a positive charge. Reduction is the gain of electrons and the gain of negative charge. Nonmetals are generally oxidized and become cations while metals are normally reduced and become anions.

Hi guys. So we're here talking about oxidation reduction reactions which are also called redox reactions. So you might recall recently that you've learned about other types of reactions say a precipitate reaction for which the driving force is formation of a precipitate or perhaps an acid base reaction for which the driving force is formation of water. So with an oxidation reduction reaction, the driving force is the transfer of electrons which throughout this section I'll denote as e-.

So redox reactions usually occur between metals and non-metals to form an ionic compound in which the metal becomes a positively charged ion or a cation and the non-metal becomes a negatively charged ion or an anion. So you'll recall from your knowledge of the periodic table that metals group one and group two elements usually become cations and non-metals from your, the right side of the periodic table become negatively charged ions. So because we know that the conse- because we know the conservation of matter tells us the electrons are neither created nor destroyed, that means that in a redox reaction, oxidation and reduction must be coupled. So you cannot have one without the other.

So what is oxidation? Oxidation is the loss of electrons, or you can also think of it as the gaining of a positive charge. Reduction is the gain of electrons or the gaining of a negative charge. So you can guarantee that this is going to be a little difficult for you in the beginning to remember that reduction is the gaining of a negative charge. So there is a simple way in which to help remember this. And that is by understanding this [IB] OILRIG. So oxidation is losing and reduction is gaining. Okay. So when something is oxidized you lose electrons or gain a positive charge. When something is reduced, that means you gain electrons or you gain a negative charge.

So here's a very simple reaction to illustrate this point. So here we have magnesium which has an overall zero charge and it goes to form magnesium 2+, right? So that means that in order to go from a zero charge to a 2+ charge, we must have lost two electrons. So that means that magnesium was oxidized. It lost electrons. On the converse of that, oxygen gained a 2- charge. Okay, so that means that it actually gained two electrons. It gained a negative charge. So that means that oxygen was reduced. Here just so we're clear, these brackets are just so I can show the charge on each of the respective elements after they've undergone oxidation and reduction. It is not a sign of concentration.

So then also, last point is that you can have oxidation reduction between two non-metals and how do you know that that's what occurring? Is that oxygen is formed as a reactant or a product. And when you have two non-metals reacting in an oxidation reduction reaction, the product is non-ionic unlike in our reaction with a metal and a non-metal. And that's pretty much oxidation reduction reactions.