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Problem 79 Easy Difficulty

A compound with the empirical formula $\mathrm{CH}_{2}$ was found to have a molar mass of approximately 84 $\mathrm{g}$ . What is the molecular formula of the compound?

Answer

$\left(\mathrm{CH}_{2}\right)_{6}(\text { or }) \mathrm{C}_{6} \mathrm{H}_{12}$

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Top Chemistry 101 Educators
Morgan S.

University of Kentucky

KS
Karli S.

Numerade Educator

JH
Jacquelin H.

Brown University

Jake R.

University of Toronto

Video Transcript

Okay. This time we need to find the molecular formula for a compound car protection compound here with NPR for coal formula. So siege to all right. And we've been given them working formula because we always need of 84 grams per mole. No. Huh? And this will help us find easily. Find the molecular formula, which I will call c x age two x two x because no of the Moeller ratio off carbon hydrogen element in the compound. So, for every more carbon, we have two moles of hydrogen, so x two ETS a double, whole more issue. So as before, we will find the molecular formula of molecular weight. Sorry of thes empirical formula. So we have one carbon Adam in this time to hydrogen atoms. So we know that the molecular weights just to some of this up just some here. So we know the Michael would give their weight of carbon, who's 12.107 grams per moan. And for Turgeon's we just, um times to off the molecular weight of an atom, which is just basically one. But I want to beat us move. They will pariahs, accuracy to find what x is and that's all. Forget units. Grant. Promote. Yeah, uh, we take a calculator, this sums up. You can imagine to being 14. Exclude the doesn't first point teen 14.26 by they grams promote. Okay, so this is the molecular weight for the empirical formula. And here is the molecular rent of molecular formula. A lot of molecular. So to find x be always divide to Michael the mercury of the molecular formula by that of the empirical formula. Grams, You know Pramono, Of course they need it. So they cancel out. And this basically gives us 5.98 which retain assume to being six. This is all an approximation or yes, it's not, like, exact exact, but all of the other an approximation just because it how that this number isn't so doesn't have this most unions 84. They didn't know at the actual molecular the most accurate, like the rate of this compound. So that's why we allowed to approximately around like that not too much of a of an approximation. Just a simple around him to the nearest integer. So now that we know x in six, that leads us to the molecular formula. Blue Sea six, age 12. Don't forget here the hydrogen is double. What? The carbon iss can you?

McMaster University
Top Chemistry 101 Educators
Morgan S.

University of Kentucky

KS
Karli S.

Numerade Educator

JH
Jacquelin H.

Brown University

Jake R.

University of Toronto