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Problem 121 Hard Difficulty

A 1.2569 -g sample of a new compound has been analyzed and found to contain the following masses of elements: carbon, 0.7238 g; hydrogen, 0.07088 g; nitrogen, 0.1407 g; oxygen, 0.3214 g. Calculate the empirical formula of the compound.

Answer

$\mathrm{C}_{6} \mathrm{H}_{7} \mathrm{NO}_{2}$

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Top Chemistry 101 Educators
TD
Theodore D.

Carleton College

Allea C.

University of Maryland - University College

Morgan S.

University of Kentucky

JH
Jacquelin H.

Brown University

Video Transcript

in this situation, we have an unknown compound made up of these four elements. I'm listing carbon, hydrogen, nitrogen in oxygen. All right. And we've been given the total mass of these four compounds to be one point to see life. Six, 8569 grams. This is the mass of this unknown compound made up of these moments where we're to find the molecular formula of this copper. What? We We've been given the mass of each element. Yeah. So in this column here, I'm gonna write math. It's so for carbon. We have 0.2 0.7238 grams compound. Just meet up with this. Wait. Carbon for hydrogen. It zero wounds zero 7088 grams for a nitrogen. It 01 for, 07 grams. And then for oxygen, it 0.3 214 Gramps. And then we already have the total at the bottom. Oh, So how are we can't find the molecular for to find the molecular formula. We need to know how much of each Adam is present. So we used to know the ratio. The other. Each element is in relative to one another. so to find that we need to work in walls in the equation for moles, formula is mass divided by molar mass capital and all right, Sarge, gonna about, uh um Gerada table and divide these masses by the molar mass of each element. So for carbon, it's this mess over 12. I went, 01 grams per mole. And here I'll just list out what the calculation equals. So is your plaint. Six year, two moles, carbon certainly have for hydrogen will take that mass over there and divided by one. Well, basically equal 2.7. When then, If we use all the 66 we can get a more accurate number. And for a nitrogen, take this number and divide it by forging grams per mole. That gives us 0.1 the oxygen Take this number and divided by 16 grams per mole and we get 0.2 So all right, here we have the molar ratio of each. Um, when will our amount of each item in this compound So this could be the sub scripts we used, but we need to work in integers. In order to do that, we will take our smallest number here and divide it. But each of these other numbers to find, like what? The whole number issues and will assign the smallest number to be one. So what we'll do now is take 0.2. You want me say divide I zero point 0.1? Yeah. Take these numbers of highway 0.1 to find, you know, an integer value. So then, for nitrogen, we would get one just 0.1 about by sequins. Everyone I hear believe need a cartel later. Supine 02 divided by 0.1 is simply too. And for Urban 56 I just wanted be seven relatively. So there we have it. These are the sub scripts for this, um, compound. All right. Here. So it was carbon six hydrogen, seven engines, one nitrogen into oxygen's. This is our compound

McMaster University
Top Chemistry 101 Educators
TD
Theodore D.

Carleton College

Allea C.

University of Maryland - University College

Morgan S.

University of Kentucky

JH
Jacquelin H.

Brown University