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Problem 38 Medium Difficulty

What is the molecular formula of the molecule that has an empirical formula of ${CH}_{2} {O}$ and a molar mass of 120.12 ${g} / {mol}$ ?

Answer

$\mathrm{C} 4 \mathrm{H} 804$

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Stephanie C.

University of Central Florida

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University of Maryland - University College

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Video Transcript

remember that the empirical formula has the lowest ratio of all the atoms in the formula. Where is the molecular formula is the actual formula, So it's usually a, uh, a multiple. I'll be adhered before meals. So if we're given the empirical formula of C H 20 and we're told that it has a molar mass of 1 2020 12 grands formal, then what we want to do here is figure out each individual grants formal for each element and just kind of add that up. And that's going to give us kind of like an empirical version of this cough house. So let's aren't carded. We know from the periodic table that there's 12.1 grams per mole and that there's only one car be present here. Let's take. There's two version present here in the incurable formula. I mean, you know, the higher should hasn't something massive 1.1 burger and crumble. We're just gonna get us 2.2 and then for oxygen. There's one oxygen president we know from the periodic table, its atomic masses. 16 grams Permal. If we add all this up and sergeant give us kind of like a pier cold mass off 30.3. All right, grants formal. So simply to convert from this empirical formula and we want to know the molecular formula, Uh, we just kind of want to know we're just going to buy the 1 20.12 brands from old that we know This compound has divided by this 30.3, and that's going to tell us the ratio of each number or kind of like the multiple of each number that we have. So we take that 1 2012 graze from all 5 30.3 grands formal. That's gonna give us forward. There's no unit here. It's just kind of like a factor, like a most location factor. So we know now that for the empirical formula, we would multiply everything by four that's going to give us the molecular formula. So let's go ahead and write that out. We had one carbon the year before. We're gonna have four carbons out in the molecular. We had to hide regions in the empirical formula, most by that, by four, we're gonna get eight hydrogen in the molecular formula, and then oxygen. If we only had one oxygen in the empirical formula we multiply that by Fuller since he was four. Oxygen's in the molecular formula. So the molecular form off of this compound is ch four. Sorry, C four h eight 04

University of North Carolina at Pembroke
Top Chemistry 101 Educators
Stephanie C.

University of Central Florida

Nadia L.

Rice University

Allea C.

University of Maryland - University College

Jake R.

University of Toronto