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Electrolysis - Concept

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.

Electrolysis is a process in which electrical energy is used to produce a chemical change that would not otherwise occur. First, an electric current is produced from a chemical using a oxidation-reduction reaction. Then this electric current is used to produce a chemical change. An example of electrolysis is hydrolysis, or the splitting of water into hydrogen and oxygen.

This segment let's go ahead and discus electrolysis which kind of falls under the broader category of the oxidation reduction reactions. So again when you hear oxidation reduction you should think that oxidation is losing of electrons and reduction is gaining of electrons. That will really help you to navigate your way through this topic a little bit.

So before we really get into electrolysis, let's kind of discuss what the broader topic of electrochemistry is and what that means. So electrochemistry is just the study of the interchange of chemical and electrical energy and a very simple example of that are batteries that you use everyday. So basically they create a redox reaction and to produce an electric current. Okay. so, it's alive and well in all of life.

So then more specifically under electrochemistry we have the process of electrolysis. So that's when electrical energy is used to produce a chemical change that would otherwise not occur. So for example if you forced a current through water to produce hydrogen gas and oxygen gas. And that reaction looks something like this. We have two waters. Add in some electrical energy and you get two mols of hydrogen gas and one mol of oxygen gas out of that. So there are two process, two types of processes are involved in this electrochemistry or in this electrolysis process. So the first is production of an electric current from a chemical and that's done by inducing a redox reaction.

The second is to use that electric current to actually produce a chemical change. So we call that half reactions, help you look at and keep track of the movement of electrons so you have a species that's being oxidised usually a metal and a species that's being reduced usually a non-metal and those two things work together to give you a redox reaction. Okay. And if you write the half reactions then you can specifically look at how many electrons are being moved back and forth between the two elements or two species, okay. So from a redox reaction you can harness that chemical energy. Okay. So then in that you'll have what we call an oxidising agent or the electron acceptor and a reducing agent or the electron donor. So try not to get oxidising agent and reducing agent confused with which one is actually being oxidised and which one is being reduced.

Okay. So you can put these two things and then separate the oxidising agent and the reducing agent and then have a way to basically watch the electrons being transferred from one to the other and you can connect them to some kind of device of your choosing to make it do work. So basically you use the electrons to produce the energy and harness that energy. So a basic application of electrolysis that happens in everyday life, it's useful for producing metals from their ores and so, one of the most common ones is aluminium. And so you can take aluminium ions with a 3+ charge and they'll be reduced and you get an aluminium solid out of that. Okay.

So I wrote the electrons on this side because it's being reduced which means it's gaining electrons and then after you get this aluminium solid, you can, or aluminium metal, you can alloy that with other metals depending on what it is you're planning on using the aluminium for. Some possibilities are zinc and manganese. And those are the most common.

And that is the basics of electrolysis.