The compound X Y Z3 has a molar mass of 100.09 g and a percent composition (by mass) of 40.04 %

The compound X Y Z3 has a molar mass of 100.09 g and a...

Key Concepts

Percent Composition Analysis

This concept involves determining the mass percentage of each element in a compound. By understanding the distribution of elements by mass, one can correlate these percentages with the element's atomic masses to determine the relative number of atoms present in the compound, which is essential for deducing the empirical formula.

Molar Mass Determination

This concept relates to the total mass of one mole of a substance. It is used to connect the computed stoichiometric ratios from the percent composition analysis to the actual number of atoms in the compound by comparing the calculated empirical formula mass with the experimental molar mass.

Empirical Formula Calculation

This concept involves finding the simplest whole-number ratio of the elements in a compound based on the percent composition data. By converting each element’s mass percentage into moles and then determining the simplest ratio, the empirical formula, which is the lowest whole-number representation of the composition, is derived.

Molecular Formula Determination

This concept extends the empirical formula by using the molar mass of the compound. Once the empirical formula is established, comparing its mass with the given molar mass helps in determining if the compound exists as a multiple of the empirical formula, leading to the accurate molecular formula.

Transcript

00:02 All right, so here we have two unknown compounds and we are to find the mass percent of each element in this compound and in this one.

00:12 So these are two separate compounds and they're unknown because they don't even have like proper chemical symbols.

00:18 They're just using xyz to replace the proper ones.

00:22 All right.

00:24 So if we look closely at this compound in this compound, we can see that each element, that this element is a multiple of this element in terms of you know this compound is a multiple of this compound in terms of number of each atom so it was as though we just took this one and multiplied by two to get two times two four one times two two two three times two six so we can say that they have the same empirical formula this guy being the empirical formula, you know, the simplest molecular formula, simplest chemical formula using integer values.

01:12 And not only would they, do they have the same empirical formula, but they also would share the same mass percent of each element.

01:23 So here they've given us the molar mass of each of these unknown elements.

01:27 So to find their mass percent, so we need to remember what mass percent.

01:32 Is.

01:33 So it is very like the name, much like the name says, the mass percent of each element in the compound, but for one mole.

01:43 So it's like mass of this element, divided by the mass total, but for one mole of compound, so that's always the key here, one more.

01:57 So it's like a mass calculation, but for one more.

02:04 So we need to then to work with mass, and they've already given us the molar masses of each element, and we know that we're always working with one more.

02:13 So then we know then if we have one mole of compound, this is the one, that we then have two moles of x, you know, the elemental subscripts over here, the number of x atoms we have, does tell us, us it's moles so and y over here it's one we have one y atom per you know compound and then for z we have three z atoms for one compound so that will then tell us no moles so then everything here is in grams per mole in this column of the table just put that in brackets and these are all moles this is a table so to then solve for mass we just need to multiply mass by molar mass uh moles by molar mass sorry n by m and once we make that division we get mass so x would be as you can see like 80 82 .4 and y would just be 57 .7.

04:00 These are all grams...

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