 Let's do this determining the half-life of a first-order reaction. It's a cyclopropane. It's the smallest cyclohydrocarbon because its 60-degree bond angles reduce overlap. Its bonds are weak. As a result, it is thermally unstable and rearranges to propane at 1,000 degrees Celsius via the following first-order reaction. They show this reaction. This reaction is 9.2 per second. So we wrote that down here. What is the half-life of the reaction? Let's figure that out. So do you guys remember the equation for the half-life of the first-order reaction? L of 2. Very good. L of 2 divided by k. So what units are we expecting to get for seconds? And is that an appropriate time unit? Okay, so if our units are good, then we're probably doing something right. Remember, L of 2 is something that you kind of use a lot, so I tend to remember it. 0.693 divided by k, which is 9.2 per second. So we're going to get seconds over here. And then the second part of the equation where the question asks, how long does it take for the concentration of cyclopropane to reach one quarter of the initial value? So remember, it's not dependent on reaction concentration, right, first-order. So how long did it take to reach half of the value? Two seconds. Right there, right? So we're going to have to do two times that, right? So it's going to be what? The time to reach a quarter was going to be the half-life times 2. That's going to be our new time. Is everybody okay with that? Yes. Can you just divide by 2? Pardon? Can you just divide your answer by 2? You're going to have to multiply by 2. Because it's how long does it take to get to a quarter? That would be how long did it take to get to half of the half-super? So two times 0.075 seconds. So when we do that, well, so that's how long it would take to get to one quarter of your original start. Everybody okay with that? Questions, questions, questions.