This one says, because it has a non-cluidine combustion product, which is water-fugur, hydrogen gas that is used for fuel above the space shuttles and in earthbound cars with prototype engines, in the reaction that's shown up here. So, let's express the rate in terms of changes of hydrogen gas concentration, and water gas concentration over time. So, how do we do that? Remember the rate, and so in this case, with hydrogen, can you guys help me out? What is it going to be? Negative one and a half, very good, times what? A change of the concentration of H2 divided by L2. Everybody okay with it? So, what would be the next one, and what's the next one? It wants us to do oxygen. So, what would oxygen be? Somebody else? Change of concentration of the oxygen. I think it would be the next one. Times, yeah, negative one, right? Like that? So, everybody okay with that? So, notice what I'm doing here, this is equivalent to that. So, we can actually set these two equal to each other, and we would want it to, too. And that's what we're going to do in heartbeat of this problem. Okay, so let's do water vapor. What is the event? So, it's going to be also equal to one. Which one? A, yes. I'm going to change it. I don't know what it is. Okay, and then it says when oxygen is decreasing at 0.23 moles per liter second. Okay, so the concentration of oxygen is decreasing at 0.0, up to 0.23 moles per liter second. How fast is water increasing? Okay, so how do we do this problem? Well, let's just erase this part here, because we have an equation here. So this, this. Okay, so we're looking for, so delta T is going to be the same, right? So we can cancel that out on each side. You guys see that? Delta T is equivalent to delta T. So effectively, what do we got? We got negative change of O2 equals one half times the change of H2 up. So everybody okay with that? Okay, what do we know about the change in O2 concentration? It's going to be negative 0.23 moles per liter second, right? Okay, so what would be the change in water concentration? So, negative 2 times the change in O2 concentration. So everybody okay with that? It's re-arranging with it. So what do we do that? Negative 2 times the negative 0.23 moles per liter second. Would you expect the water concentration to be increasing when the oxygen was decreasing? Yes. So is this going to be the correct answer? That's positive. It's going to be 0.46 moles per liter second. Is everybody okay with doing something like that? Any questions? Wonderful. Good job, guys.