 Today I'd like to talk to you a little bit about gas stoichiometry. And gas stoichiometry really is just as simple as any other type of stoichiometry. It works almost exactly like every other form of stoichiometry. One thing I'd like to discuss before we begin the actual stoichiometry has to do with the concept that's called Avogadro's Law. And Avogadro's Law is actually used to derive the following relationship. And it says that that a gas at standard temperature and pressure will occupy 22.4 liters for every mole of that gas that's present. Doesn't matter what gas. All gases would occupy this same volume. The difference in the gases would be the mass of the gases that would occupy that quantity because of the gas density. So I wanted to point that out to you. That's a factor that that comes through a lot of times when we're relating volume of gases to moles. That's STP. The next concept I'd like to talk about briefly is Galasex Law. Galasex Law says that at a given temperature and pressure the volumes of gases that react with each other can be expressed in ratios of small whole numbers. And what this means essentially is that we've always stressed to you the importance of balanced equations. And the balanced equations can be used to predict the volumes of gases that will be needed in a reaction. If we balance this reaction we find that we would have three hydrogens plus a nitrogen giving two ammonia. When we do this process we can state it another way. We can say that three moles of hydrogen will react with one mole of nitrogen to form two moles of ammonia. That's the second way that we can say this. According to Galasex Law we can take another step and we can say that if these gases are at standard temperature and pressure that three liters of hydrogen will react with one liter of nitrogen to produce two liters of ammonia. Once again the reaction has and this law has very practical terms. Let's think about this a minute. If we combine three liters of hydrogen and two liters of nitrogen that's four liters. That would also be in terms of moles it would be the same it would be a certain number of moles wouldn't it? We are adding four liters of reactants. We're getting two liters of product out. So my question would be what's going to happen to the pressure in the reactor as this takes place? Obviously based on the fact that that you're losing volume you're going to also be decreasing your pressure as well and that's a practical application for people that are building reactors.