Composition

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##### Top Chemistry 101 Educators ##### Stephanie C.

University of Central Florida  ### Video Transcript

So here we have five compounds and we are looking for who the number of molecules present in each of these compounds. Given either a mass or number of moles, let us recall, um, the formula of one number of molecules. So we know it to be moles multiplied by. I have a gorgeous Constance, right. And in case we don't have a moles is in a lot of these cases, we know that moles is equivalent to mass over molar mass. So then, if we steps to two moles in this formula over here, we get that molecules is equivalent to mass over molar mass multiplied by average. Guardo's Constance. Right. Okay, so here, first off, we have a sugar mama. It's being glucose. Could be believe black Tosi ounces to be anything but to find number of molecules we're gonna take this month, divided by its smaller mouths Among public have the guard just constant. So the molar mass of glucose is 180 0.15 grams per mole. Sorry, but and we're going to multiply that by ever. Gaja is constant and a which is the six 0.0 true true times 10 to the 23 in units of Permal so moderate that out because it's a bit too long. The EU No, I'm talking about So this then gives us one point. Hold up. This thing gives us one 0.15 times 10 to the exponents. 22. Adams, right of glucose presidency is a large number. Next on up Adam's Ari molecules molecules Items would be something a bit more complicated. Okay, next up, we have sugar again, but this time directly been given most. So you will just use this formula and multiply moles. But I have a gorgeous constant to get molecules. So you just hate that multiplied by any to get number of molecules. Atoms. Right. So this gives us to 0.7 77 times 10 to the exponents, 24 molecules of sugar. Aluko's right. So next up, we have I died. Tend to chloride very interesting compound from 25 grams of it. So then we will use this formula here that we drived and take mass The vital by the molar mass of I'd like to your floor Penta for chloride, which is 200 21.89 grams per mole multiply that by I have a gorgeous constant to give us the product of 6.78 times 10 to the exponents. 22 molecules. All right, Next up, we have a diver Might, um, hacks of high dried So, uh, have e THX die brown my heck, So I dried so one gram of it. So we will take the mass divide about a more mass, which is 27.67 grams per mole, and then multiply this. But I have a gorgeous constant, which will then give us a number of molecules. 2.17 times tend to the exponents 22. Okay, last self. We have aluminum, no tree. And here we have one more 10.5 mil Imo's. So it's time for unit conversions. So we just need to him all supplied by the unit conversion ratio. That is equivalent torm. So as the prefix Millie clam, it states we know that one more off compound is equivalent to 1000 minimal of the same compound because that's equivalent. This ratio unit conversion ratio is a call it one. So we're not changing anything about this number. We're converting. Okay? Now that we have moles, it will just multiply by Avago just constant to give us number of molecules as 6.32 times tend to the exponents 20 molecules. Right? And when you see this E, remember that it? It's times tend to the exponents. 20. Not this to explain in 20. Yeah, Depending on your calculator, you probably even have an e function, so yeah. McMaster University

#### Topics

Composition

##### Top Chemistry 101 Educators ##### Stephanie C.

University of Central Florida  