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# A compound with empirical formula $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{O}$ was found in a separate experiment to have a molar mass of approximately 90 $\mathrm{g}$ . What is the molecular formula of the compound?

## $\left(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{O}\right)_{2}(\text { or }) \mathrm{C}_{4} \mathrm{H}_{10} \mathrm{O}_{2}$

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Okay, this time we have compound see to H five. Oh, and we need to find the molecular form A. This is the imperial formal on me trendy molecular formula, which I will call two X C two X age five bucks and O s. All right. I'm doing this because these sub scripts or number of elements is giving us, like a Moeller ratio of each element in this compound. So for every two moles of carbon, there's five moles of hydrogen and there's one more oxygen, so x x x, and, you know, morally shoot. All right, as we know before, exe to find X going to do is to buy the molecular formula by the internal form. So they've already given us this molecular formula as 90 90 guards parole. And we can easily find careful for the molecular formula or the muffler. Wait. Sorry. Yes, or this guy's empirical formula. Right? So we have two carbon atoms, and we know that if you look at our periodic table, the molecular for carpet 12 01 of seven. Oh, I know seven grands Permal. And now we have hydrogen molecular formula for an Adam from all of for hydrogen is 1.794 gas for more. Just say that I thought, you know the units. And then oxygen is just 15 like 999 after a lot of practice. Well, you will be able tow, Memorize all these molecular weights. Yes. You know, grams for more. So then some of all of this equals 45 point. Oh, sits. Zero fire, if you remember what I said a couple minutes to go X in The molecular formula is a division between with much lower rate of the molecular formula over the Markkula rate of the empirical formula. So you can already see. But it's simply 90/45 which even vote calculator mean about to be to approximately two on the so grams from all you know, it's too. So you just need to do some simple multiplication to find the, you know, molecular formula. So two times, too, You know, it's 45 times to 10 2 times 12 So then army like you What formula was Just see for H 10. Oh, too. Uh huh.

McMaster University

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