Calculate the mass of carbon in grams, the percent carbon by mass, and the number of individual

Calculate the mass of carbon in grams, the percent carbon by...

Key Concepts

Molar Mass Calculation

Molar mass calculation involves determining the mass of one mole of a substance by summing the atomic masses of the atoms in its chemical formula. This is essential for converting between the mass of a sample and the number of moles, which is a fundamental step in chemical stoichiometry.

Percent Composition

Percent composition by mass is the calculation of the mass percentage of each element in a compound. It is determined by dividing the total mass of the element in the formula by the molar mass of the compound, then multiplying by 100. This is important for understanding the relative amounts of each element in a compound.

Mole Concept and Avogadro's Number

The mole concept provides a bridge between the atomic scale and the macroscopic scale by defining a mole as 6.022 x 10^23 entities (atoms, molecules, etc.). Avogadro's Number is used to convert between the number of particles and the amount of substance in moles, which is critical when calculating the number of individual atoms present in a sample.

Chemical Formula Interpretation

Interpreting the chemical formula allows for the identification of the number of each type of atom present in a molecule. This information is crucial for both calculating the molar mass of the compound and determining the fraction or number of atoms of a specific element in a given sample.

Transcript

00:01 All right, so here we have three compounds, carbon -containing compounds.

00:08 We have over here phenol, which is like benzene with an alcohol group, if that means to sense to you, or don't worry about it.

00:16 We have carbon monoxide and tri -carbon dioxide, known as carbon -siboxide.

00:25 So, that's not too worried too much about the names, but let's just try to solve.

00:32 Some things over here.

00:33 So they've access to find mass percent of carbon, just of carbon, which let's just quickly remind yourself of that formula.

00:48 It would be basically the mass of carbon over the mass of the molecule.

00:55 If we simplify it.

00:59 Now let's go m for molecule, see for carbon.

01:03 Now let's go a step further.

01:07 So it's not just any regular mass.

01:11 It's the mass of one mole of compound.

01:15 So we know that mass is equivalent to moles multiplied by molar mass, and we are always working in one more.

01:25 Yes, always one mole.

01:29 This is the standard.

01:32 One mole of compound or molecule and one mole of whichever element carbon here.

01:40 So then we just multiply the moles by the molar mass of carbon over the molar mass of the compound.

01:50 Yeah.

01:51 Okay.

01:53 So that's how we're going to solve for the molar mass or the mass percent of carbon.

01:59 So we're also looking for the number of atoms of carbon.

02:10 So so to find that number of atoms, number of atoms is always related to number of molecules.

02:32 So let's just first copy down the number of molecules formula, which is just n for moles multiplied by n a, avogadro's constant.

02:44 Okay, this right here would give us number of molecules.

02:48 But we then have to multiply by, i'll just call, we have to multiply by the particular number of carbon atoms in the compound.

03:08 So let's just put brackets and say number of carbons.

03:20 Number of carbons.

03:22 Right.

03:26 And they were also asking us lastly for the mass.

03:29 Mass of carbon, it could have to be quite weird.

03:33 So here is the mass of carbon suboxide, but they want to know the mass of just the carbon in this compound.

03:42 So it might be a little tricky, but the way we would solve for that is just take the total mass and multiply it by the mass percent of carbon.

03:53 It's the simplest way to do it.

04:00 Right.

04:01 So let's get started.

04:05 I have quite a lot to do.

04:07 So we must find number of atoms of carbon, mass of carbon, and the mass percent of carbon.

04:19 Okay.

04:22 So right now we have, for this compound, we were given total mass.

04:27 So let's start off by finding the mass percent.

04:31 So i have simplified the mass percent formula.

04:45 So these basically cancel out.

04:50 It's okay.

04:51 And all we're left with is mass of carbon over mass of molecule.

04:58 See for compound, but that's a bit too confusing.

05:01 Let's just call it molecule.

05:04 So here we're going to need our periodic table, but i know the molar mass of carbon, is you should.

05:11 Should know as well it's just 12 and i'm also not going to use units because this is a mass we're talking about the mass equivalent to a molar just use the property in its grams and the molar mass of this carbon suboxide is 68 then if we were to multiply each of these molar masses by one mole then that's how we get them to be grams but since it's just one more and we can cancel that out.

05:58 Now, this gives us a mass percent of 52 .9.

06:10 Here we have it.

06:11 The first answer, 52 .9%.

06:17 So then to find the mass of carbon, we'll take the total mass, which was like 7 .819, and multiply that by the mass percent in a decimal not in a percent thing and this is grams this will give us a massive carbon of being 4 .14 grams okay and lastly what we're looking for atoms number of atoms so let's just use this space number of atoms it's equivalent to moles times avagatres constant the number of carbon atoms in one compound.

07:21 Okay, so we don't have moles, but we do have, we do know that most is equivalent to mass of a molar mass, and we have the mass.

07:37 And here, this would not be the mass of carbon, no way.

07:41 This is, you know, the mass of the compound.

07:43 We're going to adjust for this to be like just carbon by multiplying by this factor over here.

07:52 This is still total moles of the compound.

07:55 This factor will adjust it to just be carbon.

08:00 That makes sense.

08:01 I think it does.

08:04 So that's na for our godgers number times number of carbon items which is just this little subscript which is three.

08:14 Okay so let's just quickly plug this all these figures in.

08:20 We have mass over molar mass again.

08:26 Of the whole compound which is over here we saw it to be 68 grams and grams per more i'm not going to write out avagadroa's constant you know it's 6 .0 it's 6 .022 times 10 to the 23 and then multiply this all by 3 to give us a very large number let's see.

09:07 This is going a bit messy.

09:09 It's all equivalent to 2 .07 times 10 to the exponent 23.

09:24 So yes, quite a lot.

09:30 Just make that a little bit neither.

09:32 So yeah, these are, this would be atoms of carbon.

09:37 It's just highlighted.

09:44 Yes, it does work.

09:46 So these are the answers.

09:48 In green.

09:52 Right, so let's move on, and let's try it to do this a bit quick.

09:56 All right, so here we have a number of carbon monoxide molecules.

10:05 So we can straight ahead jump into number of atoms, whichever, you know.