 And in this one we're going to specifically look at reaction conditions. So probably the best one to look at when we're talking about reaction conditions is the Haber process. So this is a process in which nitrogen and hydrogen are combined to form ammonia. This is one that we're a little bit familiar with. It's an exothermic reaction in the forward direction. It's also an equilibrium system. And so it allows us to have a little bit of a look at the specifics of this process. We can talk about this as we talked about previously, the availability of reagents and therefore nitrogen we could get from the air. Hydrogen can be generated in a number of chemical reactions. And of course we do need to be aware of our reaction conditions because the problem with sourcing nitrogen from the air is that there is also a fair amount of oxygen in the air as well. And we do know that hydrogen and oxygen when they combine together are explosive. And so therefore if we are going to source the nitrogen from here we just need to be aware of the fact that we either have to do something about the oxygen or we need to control the process very carefully. The Haber process also uses a catalyst which is magnetite. But more importantly our understanding of equilibria or equilibrium systems allows us to manipulate the conditions in different ways in order to help us to maximize the yield that is to get as much of the ammonia as we possibly can. So when we work through this list our manipulation of the conditions are such that we can evaluate the changes in any of these particular variables and then work out how Le Chatelier's principle can be applied to see how the system will shift. So for example the fact that we know it's an exothermic reaction means that we will increase the yield if we decrease the temperature. So this favors the forward reaction. Now that's fine and that means we will increase the yield unfortunately if the temperature drops too low then the reaction rate will also drop with it and as a consequence we may have increased yields but we may be taking more time to actually reach those. So often we use a compromise something that sits somewhere between a high temperature which increases the reaction rate but not too high a temperature that drives the reaction too far to the left. The same is true with pressure. So what we have when we look at pressure is we have 1 plus 3 is 4 moles of gases on the reactant side and just the 2 on the product side. So therefore an increase of pressure will also favor the forward reaction and again increasing the yield. Now this is great we can just increase the pressure and increase the amount of ammonia that we produce. The problem of course is once again if we have pressures that are getting too high then we may have some issues around safety. We also may have issues around cost and so therefore there has to be something that is again like temperature a compromise that allows us to maximize our yields but to do it in a way that respects the plant itself, the safety of the workers, the safety of the equipment and also keeps our costs down low. Another thing that we can do is to look at concentration. Concentration is also something that affects an equilibrium position so obviously we can increase the concentration of the reactants and that will send it to the right. We can also decrease the concentration of the product and we can most easily do that by liquefying the ammonia and if we do that then that is going to come out of the reaction vessel as a gas. It will liquefy as that's the highest boiling point of all three of these species and therefore we can withdraw it, decrease the concentration of ammonia and drive that reaction to the right. The important thing when you're evaluating reaction conditions is you think about whether or not we use a catalyst, how we manipulate conditions like temperature and pressure, how we are able to change concentrations in order to help us to maximize the yield that we have for each of these different reactions. As I say I really think you need to be given these equations in order to evaluate these sorts of factors but make sure you keep all of these things, take all these things into account, even something like if we're doing esterification and you're looking at reaction conditions then you're often going to talk about something like refluxing which is a condition under which that particular chemical reaction is carried out in order to address a number of different factors associated with that reaction. So these are the sorts of factors that you're going to be looking at when you are considering reaction conditions. Practice them on a few different examples and thanks for watching.