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Numerade Educator



Problem 111 Hard Difficulty

Which of the following models represent compounds having the same empirical formula? What is the empirical formula mass of this common formula?


$\mathrm{B}, \mathrm{C}$ and $\mathrm{D}$ have the same empirical formula.
$\mathrm{Mr}=44,02 \mathrm{g} / \mathrm{mol}$


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Video Transcript

there are different ways in which we can describe the composition of a compound. Given its formula, an empirical formula is the simplest lowest whole number ratio of atoms in a molecule. The molecular formula is the actual ratio of atoms in a molecule. Usually it's a multiple of the empirical formula and finally, the most informative. And the images that you're given in this problem are structural formulas, which are pictures that show which Adams are present, as well as how they're connected. Typically in structural formulas, the black circles represent carbon. The red circles represent oxygen, and the blue circles represent hydrogen. So if we look at each of these images, we confined the actual molecular formula from the structural formulas the spread company. So if we look, for example, at molecule A, our molecular formula IHS C four h 10 Oh, too. Just by counting, we look it be. We see that the molecular formula is C two h four Oh, CSC for each eight. Oh, too. De has six carbons. So it's C six h 12 03 and finally ease C five hte eight. Oh, too. These are the molecular formulas to find the empirical we reduce the ratio is the lowest whole number ratio. So here I can divide each one by two C two h 50 This is the empirical formula. This is already in its lowest whole number ratio. So C two h 40 the empirical formula here I have dividing each by two c two h four. Oh, here I divide each by three See to H four. Oh, and finally, this is also in its lowest whole number ratio. So the molecular formula is the same as the empirical formula. So we can see that while we have prive different molecules be c and d have the same empirical formula and we can find the formula mass simply by adding up molar masses of each element in that empirical formula. And so one more is equal to two times the molar mass of carbon, which is 12.11 found on the periodic table plus four times 1.8 plus 15.999 you for oxygen or 44 0.5 grams. And so the formula mass is 44 0.5 grams per mole