 Let's do one of these determining a reactant concentration at a given time reaction. So it says at 1,000 degrees Celsius, cyclobutane, which is C4HA decomposes in a first order reaction, which we should have already known by looking at the units of K here, okay? So that, since it's seconds to the negative one, we should realize that it's a first order reaction already, with a very high rate constant of 87 per second to two molecules available. If the initial cyclobutane concentration is 2 molar, what is the concentration after 10 seconds? So if you remember the rate law equations that we just went over, okay, if you don't, just look back in your notes, okay? The first order rate law was ln of A, or in this case C4HA, the original time divided by cyclobutane, or the concentration is C4HA at time t. That equals Kt like that. So we have concentration original, we have K, we have t. So we're trying to find what is this concentration at that time. Does everybody understand what we're looking for? So how do we get rid of ln? You guys remember? E to the ln, right? So what we do to one side, we've got to do the other side. So this is going to be E to the Kt. Is everybody okay with me just erasing? So that cancels with that like that, and all of this comes down here, right? So what are we going to get? We're going to get C4HA like that, and what are we looking for? C4HAt, right? So let's rearrange this equation to get that. So we get C4H8t well, C4H8O divided by EKt, like that. Is everybody okay with me? So let's go over here with it. And just plug in Chubb now, so it's 2.00 polar divided by, so the K is 87 per second times 0.00, like that. Cancel, cancel there. What should our unit, what would you think our units would be for the concentration at time t? Mole, or moles per liter, right? Are they going to be? Yes, okay? So if you're not getting good concentration units, then you've probably done something very correct. Okay, so let's go ahead and do this. Fraction has decomposed in this time. Should we do that part too while we're doing this video? I'll let you guys write down what we have here. Can I erase at least this part up here? And we know also C4H8T is what we say. So, fraction decomposed, that's going to be what you have over what was, okay, what was the total, okay? So you had this to begin with, and this is what you have left, okay? So let's say C4H8O minus C4H8T divided by C4H8O. Does that make sense? If it doesn't make sense, maybe it'll make sense when we plug the numbers, okay? So when we got first, 2.0 molar minus 0.84 molar divided by 2.002, okay? So what we have here is C4H8T divided by C4H8O. Is that makes sense? If it doesn't make sense, maybe it'll make sense when we plug the numbers. Okay? So when we got first, 2.00 molar minus 0.84 molar divided by 2.002, okay? So what are my units? Because it's a fraction. Fractions don't have units. That's the fraction decomposed. What if it asks me, what percentage of decomposed? What do I do then? Multiply. Multiply divided by 100%. So let's say the percent decomp. Do I need to show that now? So the percentage that we have left would be 100 minus that. The fraction that we have left would be 1 minus that, okay? But are you okay with doing something like that? So again, in order to do these, you're going to have to memorize those rate laws, okay? Any questions on something like this? If you memorize the rate laws, you should be fine.