In this video we’re gonna convert moles

to mass and vice versa using two examples. We can inter-convert

from moles to mass and from mass to moles using the molar mass of that

substance. In order to perform this calculation we’ll first need to know how

to calculate molar mass. I’ll link the video on the top if you need a refresher.

Let’s try out a couple of questions to see how we can convert between these two

things, moles and mass. Let’s look at our first question. It gives us 0.245 moles and it’s asking us to find the mass of zinc. We’re gonna use

dimensional analysis method to solve this, so, we write out what we need to

find which is the mass of zinc equals what the question gives which is 0.245 moles and then we place a multiple sign and draw a line

across. Place what we want to get rid of at the bottom which is moles and then it

will cancel out like that and then we place what we need to find on top which

is the grams of zinc. We look at the atomic mass of zinc in the periodic

table and we get 65.39. So we place that next to the grams

and since it’s the molar mass is the mass for one mole that means it’s one

next to the mole. So, we do the math, 0.245 times 65.39 gives us 16.0 grams. If you don’t like solving

using this method just remember if you’re given moles and you need to find

mass, simply multiply the given number with the molar mass. Moving on to our

next and final question. This question is the reverse of the first question. It

gives us the mass and it wants us to find out moles. We’re gonna use the same

method, so, we’re gonna start by writing out what we need to find and then equals

what we’re given 392 grams and times draw a line across and then we place

grams at the bottom so that we can cancel them out. And then we place mol on top

because that’s what we need to find. Okay. Now it’s time to fill in the numbers

since we’re using molar mass which means its the mass for one mole, so, we’ll place

one next to mole and then we need to calculate the molar mass of CCl4 and

that’s 12 plus 4 times 35.45. 12 for carbon. 35.45 for chlorine which turns out to be 153.8 grams. We

take 392 times 1 and divided by 153.8 and we get 2.55 mols. Don’t forget to include the unit mol.

Again if you’re not into this way of solving, all you have to remember is in

going from grams to moles all you have to do is you divide the given mass with

the molar mass of the compound. To recap, from the two questions we’ve worked on,

when going from moles to mass we multiply with the molar mass and in

going from mass to moles we divide the molar mass. I hope the video helped you

out somehow. Do subscribe and thanks for watching!