 Okay, so let's do this problem. There was What's a question that somebody brought to me one of you all brought to me, so Let's do this before the quiz today. So this one says Ethyl chloride C2H5Cl is used as a local anesthetic It works by cooling tissues as it evaporates the heat of vaporization is 26.4 kilojoules per mole how much heat could be removed by 10 grams of ethyl chloride, okay? So we have ethyl chloride. This is all the information from the problem, right? So the mass of ethyl chloride the molecular formula and the heat of vaporization, okay? So remember chemistry, right? We just want to cancel out our units to get the units that we wanted, right? And it said How much heat can be removed, right? If I remember the exact wording correctly, so that's energy, right? So we'll just say Delta H, okay, so that's what we're looking for But we have grams and we have kilojoules per mole and remember energy That's kilojoules that unit, right? So we could if we can get that unit isolated then that means we've got the energy Okay, that we need it so In order to isolate that kilojoules we have to get rid of moles, right? But we have grams. Is there anything that we know that converts grams to moles? Yeah, what was it? The molar mass, right? Everybody's freaked out with the video on It's alright The molar mass you're absolutely right, right? How do we calculate the molar mass? We have the molecular formula, right? What will we do? Yeah, they have look at the periodic table, right? Okay, so carbon is what? So the molar mass of C2H5Cl Carbon, there's two of them, right? And we've got 12.00 grams per mole Plus hydrogen, there's five of them 1.008 grams per mole And then 40 is What? 35 40 Help me out. 45 grams per mole, okay? So has anybody added that up yet? 64.49 64.51 51 is what I think, okay? So we'll do five, we'll do five ones since that's the way I calculated it on my paper, okay? Okay, so everybody's cool with us doing this part, right? So hopefully now you can see, well, we've got something that converts grams to moles, right? And we want to get rid of moles here, so we're really set, okay? So let's just do it one step at a time so we don't get, you know, two Confused about what we're doing. So let's do a number of moles of Ethyl chloride first Okay, so we know how many grams we've got And we want to cancel out grams and get moles, right? So we're going to put the grams on the bottom, right? Is everybody okay with that? So 64.51 grams and one mole on the top Cancel, cancel And has anybody done that? Yeah Anybody got it? Is that what you got? Wonderful, wonderful, okay And then, right, so what are we looking for? Delta H, right? We've got something that converts moles to kilojoules, right? And we've got mole. Does everybody Understand what we're going with this? So let's just erase our question mark because it's no longer a question mark But our 0.155 moles of Ethyl chloride up there and then multiply it by our Ratio here that says for every one mole Of Ethyl chloride it gives Or it's able to take away I guess in this problem 26.4 kilojoules of energy Okay So hopefully everybody can see canceling out moles, moles, okay, and that's going to give us And it's a three-sink figs 4.09 So it's going to remove 4.09 kilojoules of energy Everybody okay with doing something like that? So remember it's just canceling out units, so don't get overwhelmed when you see kind of a scarier problem like this, okay? Questions before we kill it