in this video we're going to cover le chatelier's principle which is about the position of equilibrium during a reversible reaction and specifically how it's affected by temperature pressure and concentration we saw in the last video that the position of equilibrium refers to how many reactant particles there are compared to how many product particles there are when at equilibrium for example we would say that the equilibrium lie to the left if there are more reactants and to the right if there are more products now le chatelier's principle is the idea that if you change the conditions of a reversible reaction then the position of equilibrium will shift to try and counteract that change and so we can use this principle to predict what will happen when we change the conditions to see what this means in practice let's take a look at this reaction for the production of ammonia from nitrogen and hydrogen and imagine that it was being done within a sealed system the minus 92 kilojoules per mole is the overall energy change of the forward reaction and because it's negative we can tell that the forward reaction is exothermic which means it releases energy to the surroundings and because the backward reaction has to be the opposite of the forward reaction it must be endothermic for the sake of our example let's imagine that the position of equilibrium starts off here in the middle if we were to decrease the temperature of our system the equilibrium would move in the exothermic direction in order to release heat energy and counteract that change that we just made in this case that would mean the position of equilibrium move to the right so we'd have more ammonia particles and fewer nitrogen and hydrogen particles on the other hand if we increase the temperature of our system then we oppose this change and decrease the temperature the equilibrium will move in the endothermic direction so to the left which means would have more nitrogen and hydrogen but fewer particles of ammonia we can also apply this concept to the pressure of our sealed system so if we increased the pressure then the equilibrium would move to whichever side reduces the pressure back down and as pressure is basically just a measure of how many particles there are per unit of volume to lower the pressure the equilibrium will move to the side with the least number of molecules which in this case is the right because there are only two molecules of ammonia on the right hand side whereas there's four molecules on the left because there's one nitrogen plus three hydrogens on the other hand if we decrease the pressure then the equilibrium will shift to the side of the more molecules so the left in order to increase the pressure again the very last change that we need to look at is changes in concentration for example if we added more nitrogen to our sealed container it would increase the concentration of nitrogen so to oppose this change the equilibrium shifts to the opposite side which in this case is the right and forms more ammonia and that's it for this video so if you found it helpful then please do leave us a comment down below and we'll see you next time