 I'm going to show you how to use equilibrium tables, which are a tool that we can use to solve more complicated equilibrium problems later on. I'll just divide them up so you can see there are three separate problems. And if we take the first one here, you can see that we have a reaction where nitrogen is reacting with 3 moles of hydrogen to give 2 moles of ammonia, and it's an equilibrium. And we're given some information, we're told that initially 0.1 moles of nitrogen was mixed with 0.1 moles of hydrogen, and that there was no ammonia present at the beginning. And then the system was allowed to come to equilibrium, and you're given the extra piece of information that at equilibrium there is 0.07 moles of nitrogen. But you're not told how much hydrogen and ammonia there are at equilibrium, and that's what we want to work out. So what I'm going to do is put an extra row in the middle of this table, which I'm going to call moles used or produced, you could call it perhaps the change in moles. So you can see that for nitrogen we started with 0.1, we ended up with 0.07, so we must have used 0.03. You could say minus 0.03, so 0.1 minus 0.03 gives us 0.07. Now how much hydrogen was used? Well, we know that for every 1 mole of nitrogen, 3 moles of hydrogen get produced. It's a 1 to 3, sorry, for every 1 mole of nitrogen used, 3 moles of hydrogen get used. So it's a 1 to 3 stoichiometric ratio. So if we know that 0.03 moles of nitrogen were used, then we also know that 3 times that, which would be 0.09, moles of hydrogen must have been used. So the moles of hydrogen left at equilibrium is 0.1 minus 0.09, which gives us 0.01. On the other side of the reaction, we've got the products. Now going back to the stoichiometry of the reaction, you can see there's 1 mole of nitrogen ends up giving 2 moles of ammonia. So that's a 1 to 2 ratio. If we used 0.03 moles of nitrogen, then we must have produced twice as much ammonia. So that's 0.06, and it was produced, so we'll make it positive, plus 0.06. So we started with none. We created 0.06 moles, so at equilibrium we have 0.06. And that's our table filled in.