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Monosodium glutamate (MSG), a food-flavor enhancer, has been...

Key Concepts

Percent Composition

Percent composition refers to the percentage by mass of each element in a compound. It is a key concept for analyzing chemical compounds because it provides the basis for converting the mass percentages into mole ratios, which is essential for determining the compound's empirical formula.

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole. It is crucial for linking the macroscopic mass of a substance with its microscopic mole-based composition, thereby enabling the determination of a compound’s molecular formula when compared with the calculated empirical formula mass.

Empirical Formula

The empirical formula represents the simplest whole-number ratio of elements in a compound. It is derived by converting the percent composition to moles for each element, then dividing by the smallest number of moles present, and finally adjusting to the nearest whole numbers. This provides a fundamental description of the compound’s composition before scaling to its actual molecular formula.

Molecular Formula

The molecular formula gives the actual number of atoms of each element in a molecule of the compound. It can be determined by comparing the empirical formula mass with the compound’s molar mass. If the molar mass is a whole-number multiple of the empirical formula mass, that multiple is used to scale the empirical formula up to the molecular formula.

Transcript

00:01 So for this problem, we are given some percent composition of a certain compound.

00:05 We know that the molar mass of the final compound, and we want to find molecular formula.

00:12 So in general, our approach is going to be find the empirical formula for the compound, and then relate that to the molecular formula of the final compound via the molar mass.

00:22 So first, we want to find the empirical formula.

00:26 So we know that the compound is 31.

00:32 0 .51 % carbon, 4 .77 % hydrogen, or 37 ,0 .85 % oxygen, 8 .29 % nitrogen, and 13 .60 % sodium.

01:00 So, hypothetically, if the compound was 100 grams, then this would correspond.

01:06 To 35 .51 grams of carbon, 4 .77 grams of hydrogen, 37 .85 grams of oxygen, 8 .29 grams of nitrogen, and 13 .60 grams of sodium.

01:26 Now, once again, the compound obviously isn't going to necessarily weigh 100 grams, but we hypothetically assume it is because that helps us build proportion that we can, then use to find the empirical formula.

01:39 So if we have 35 .51 grams of carbon, we want to convert that into moles of carbon, and we can do that by dividing by the molar mass.

01:50 We know that the molar mass of one mole of carbon is 12 .01 grams, and when we multiply that out, we get 2 .96 moles of carbon.

02:01 Same thing for hydrogen.

02:02 You know that it's a molar mass is 1 .008.

02:07 We multiply that out.

02:09 We get 4 .73 moles of hydrogen.

02:17 Oxygen.

02:18 We know that in every mole of oxygen.

02:22 16 .00 grams.

02:24 We multiply that out.

02:26 We get 2 .37 moles of oxygen.

02:33 And then we do nitrogen.