Calculate the mass in grams of hydrogen present in 2.500 g of each of the following compounds. a

Calculate the mass in grams of hydrogen present in 2.500 g...

Key Concepts

Percent Composition

Percent composition involves calculating the mass percentage of each element within a compound. By determining the mass contributed by a particular element from one mole of the compound and comparing it to the compound’s molar mass, one can find out what fraction or percent of the compound is made up of that element.

Stoichiometry

Stoichiometry refers to the quantitative relationships between the substances in a chemical reaction or compound. It involves using the mole concept, molar masses, and balanced chemical formulas to compute the amounts of reactants and products, which in this context include calculations to determine the mass of hydrogen present in different compounds.

Mole Concept

The mole concept is fundamental in chemistry and allows the conversion of masses of a substance to the number of particles (atoms, molecules, etc.) through the use of Avogadro's number. It forms the basis for quantifying the amount of a substance involved in chemical reactions or compositions.

Molar Mass

Molar mass is the mass of one mole of a substance, expressed in grams per mole. It is determined by summing the atomic masses of each element as indicated in a compound’s molecular formula, and it is essential for converting between the mass of a substance and the number of moles present.

Transcript

00:02 Alright, so here we have four compounds, and we are finding the mass of hydrogen.

00:08 So let me write this down.

00:10 We are finding, the only thing that we're finding just one thing is mass of hydrogen, so mh.

00:17 So what we're gonna use, and we've been told that the mass total of each compound is 2 .5.

00:30 So let me put a question mark here.

00:32 That's what we're looking for, and we've been given up the mass total 2 .5 grams.

00:37 Mm -hmm.

00:43 Okay, and the formula that we're just going to use is finding the mass percent of hydrogen.

00:51 Because then once we find the mass percent of hydrogen, we multiply by the mass total, and then we get mass of hydrogen.

00:58 Okay, so mass percent is mass of hydrogen over mass.

01:09 Of the compound, but not just one mass, one more of compound.

01:25 So then that's one mole, because we know that mass is moles multiplied by molar mass.

01:34 And we're always working in one mole.

01:36 So one mole of compound, multiplied by molar mass of the compound, and then one mole of element.

01:49 Not one more element, but one more of the compound and how many ever hydrogens that could be.

01:58 So there is usually, there is going to be a factor that we're going to multiply this by for it to be one mole of compound.

02:08 So it's going to call it x.

02:15 We're still going to multiply it by it.

02:18 It's still going to multiply it by a factor.

02:22 So we're always dealing with a full mole of compound.

02:29 If that makes sense.

02:31 So first off, we have benzene, and we are finding the mass percent.

02:38 So let's start off at the bottom.

02:39 The bottom is a bit, this denominator here, it's a bit more straightforward.

02:46 So one mole multiply the mole mass of this compound.

02:49 The mole mass of this compound is like 78.

02:53 It's going to try to move fast, so i can't really write all these decimals.

02:58 Grams.

03:00 We multiplied one mole, but in one mass.

03:05 Now, for hydrogen, there's a factor.

03:09 Excuse my mistake in the previous video.

03:13 But for us to have one mole of this compound, we are going to have six as many, as more, sorry, hydrogen atoms.

03:23 So it's going to be this x number is going to be six times the molar mass of hydrogen, which is basically one.

03:32 So, we know.

03:36 Let's try and draw brackets 1 .008...

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