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Problem 122 Hard Difficulty

A 0.7221 -g sample of a new compound has been analyzed and found to contain the following masses of elements: carbon, $0.2990 \mathrm{~g} ;$ hydrogen, $0.05849 \mathrm{~g} ; $ nitrogen, $0.2318 \mathrm{~g} ;$ oxygen, $0.1328 \mathrm{~g} .$ Calculate the empirical formula of the compound.

Answer

$\mathrm{C}_{3} \mathrm{H}_{7} \mathrm{N}_{2} \mathrm{O}$

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Top Chemistry 101 Educators
Lizabeth T.

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Nadia L.

Rice University

Stephen P.

Drexel University

Allea C.

University of Maryland - University College

Video Transcript

All right. So, um, in this question, we have an unknown compound made up of these four elements where you're trying to find the molecular free. Okay, so here we've been given the mass of each element within the compound. So for carbon, it was 0.299 Corey ums, It's his own units of grams. Just bracket up top there. Haejoo, We've been giving 0.5849 grams for a nitrogen. We've been given zero point 2318 grams and oxygen this 1.3 to 8 grams. Okay, so are for us to find the amount of each element present to write the month of formula, we need to know the ratio of, like, how much of each Adam is there. So to find that ratio, we can't work with mass. We must use malls in the units more. Okay, So in order to find moments, we simply take maps and divided by Miller Mus. Right? Okay, so you know the molar mass of all of these Adams by looking at the our periodic table sold just taken this mass and divided by the molar rats. And here's what we get so for up for carbon, we take 0.2 to 9 grams and divided by the 12.1 grams per mole. And we get to a point zero or zero points your tooth for 89 moles engine. Take this number whether by the one gram per mole recently get 0.58 Your 0.0 58 0 to 9 for an estrogen will take this mass and divide it by the 14 grams. Mol, when we get 0.16 55 and for oxygen, we take this mass and divided by the 16 grams per mole. And then we get quite a small number 8.3 times 10 to the exploding negative three. Okay, so then we could use these numbers for the mullahs, Max, but not for a moment for the molecular formula. But we need to work and introduce values. Therefore, we must divide each of these moles by a constant, you know, trade into entered your and my constant that we will use is the smallest mole quantity, which is this oxygen case will take each of these malls and divided by the by the 0.8 by the 8.3 times. Tend to the negative three. So this will effectively, um, take this these molds here in tournament whole positive numbers. So we know for oxygen that would make it give it a one for nitrogen. Got a two. Once we do that division for Haijun, it's seven and oxygen of three. See? And it's with these numbers that we can form our molecular formula. It's carbon three hydrogen, seven nitrogen to with the one oxygen, Yeah.

McMaster University
Top Chemistry 101 Educators
Lizabeth T.

Numerade Educator

Nadia L.

Rice University

Stephen P.

Drexel University

Allea C.

University of Maryland - University College