 Let's go ahead and try this one. It says how many carbon atoms are contained in 15 milligrams, okay? So I have written down up here the mass of the carbon is 15 milligrams, okay? And then we look at the periodic table here, and it says that carbons molar mass, right? So the molar mass of carbon is 12.01 grams per mole Okay, so this kind of helps us to figure out what units we want that, so this since this is grams We want to put that in grams, okay? So we go like this So how many milligrams are there in one gram? Do you remember? 1,000 milligrams, yeah, so the opposite, right? So 1,000 milligrams in one gram So that cancels with that, right? And then we go 1, 2, 3, like that 0.0150 Grams, like that, okay? So now the molar mass of carbon and it's in the number of atoms, okay? So The molar mass of carbon tells us well 12.01 grams per mole and we have that many grams So let's figure out how many moles we've got, okay? So the number of moles of carbon is going to be one mole divided by 12.01 grams, okay? Because you want moles to be on top, right? So we're going to multiply that by 0.0150 Grams, like that And that's going to cancel with that and that's going to give us moles. Does that make sense? Okay, so let's do that calculation together. So the number of moles that I got and Since this is three significant figures, I'm going to round to three significant figures, okay? So 1.25 5 times 10 to the 1, 2, 3, so negative 3 moles of carbon, okay? That's how many moles of carbon we've got But it wants us to figure out the number of atoms of carbon. So atoms Well, we have to remember Avogadro's number, okay? So do you remember Avogadro's number? Okay, that's something you want to remember I'll actually give it to you on the Exam, but you'll have to know when to use it or the quits, but you'll have to know when to use it So Avogadro's number is 6.022 times 10 to the 23rd, okay? And it's whatever per mole. In this case, that many atoms per mole. So we know how many moles we've got, right? So let's write that down 1.25 times 10 to the negative 3 moles and we know How many atoms there are in one mole, right? Because it's 6.022 times 10 to the 23rd So we want to put mole on the bottom, so we'll cancel it out. So we've got one mole there 6.022 times 10 to the 23rd atoms That makes sense, right? And then we just cancel, cancel, like that And then we'll just put that on our calculator So multiply that last entry by 6.022 23 And so this is gonna be a lot of atoms, okay? So 7.5 5 2 times 10 to the 20th atoms of carbon There's a lot of atoms of carbon in 15 milligrams, okay? Does that make sense how to do it? Yeah, so all you really have to do is cancel out your units If you can do it like this just do it like how I'm doing it and if you can cancel out your units You'll get the right answer every time, okay? So I'd like you to try those other ones on your own and then see I wanted you to show me what answers you get and then we'll Check it from there. Okay. Is there any other questions on this one? No, I'll try the next one. Okay, I wonder