 Part of our final inquiry question in module 8, we are looking at chemical synthesis processes and we're specifically looking at, in this video, yield and purity. Now I have looked, split all of these different components up with a specific process to kind of focus in on those, but any of these processes could be used to evaluate all of the factors that are associated with chemical synthesis and design. But this time, we're going to be looking at the production of sodium hydroxide. Here's the equation to represent the production of sodium hydroxide. And this is actually an electrolysis process. So in this case, what we're doing is using electricity to create a chemical reaction. So that means it's not spontaneous in this direction, it won't automatically react. We're going to need to put a source of energy in order for it to react. And in order for us to obtain our goal product of this type of industrial process, which is sodium hydroxide. Now what you need to do is set up something called an electrolytic cell, which just looks like a galvanic cell, but where we've reversed the electrodes basically. So that as the electrons flow in the opposite direction, we actually get a chemical reaction to occur. To simplify things a little bit, if you consider that our two half cells that we would have, and the thing with an electrolytic cell is you don't have to separate them because the reaction's not a spontaneous one. But what we usually do is we separate them by some sort of a membrane or an alternate electrode. Three processes have been identified as being particularly important to this type of process. And we've changed them over time for a number of different reasons. Not all of which are associated with yield and purity, but they do give us a little bit of an idea of the sorts of things that we can discuss when we're thinking about this. As you'll know, I can give you 20 slides which all break down the whole process of sodium hydroxide production, but we have to think about what are the sort of things you're likely to get in an exam. And in an exam, you're going to have to have a little bit of information about each process, which you're going to have to withdraw and then use your knowledge of the factors associated with chemical synthesis and design to make some conclusions. So these are the sorts of things that you might want to talk about when you're talking about yield. We've always said that the most important thing about yield is we want to maximize it. It's important that we maximize yield when we are looking at any industrial chemical process, because that's what it's all about. It's an economic process. It's one in which we are trying to produce a quality product, but also we want to produce as much as possible to meet the demands of our markets. Purity is a different kind of a thing and purity is basically about isolating the desired product. So in this case, when we try to isolate our desired product, we have contaminants in with our sodium hydroxide and we don't have pure sodium hydroxide, and that's going to create some problems around the consistency that we have with what we're trying to sell.