Composition

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##### Top Chemistry 101 Educators   ##### Jake R.

University of Toronto

### Video Transcript

Okay, so here we have six elements which are all medals for my Lloyds, and we're to find three things about them. You are to find their mask, moles and number of items given one of those pieces of information so down below here I have written the molar mass just to help us, you know, to solve for all of these parameters. So before we can start, we just need to recall a couple equations. So we know that mass mass equals number of moles multiplied, but the molar mass and moles equals mass over more mass. Also, we know that number of atoms is equalled. Two number off malls multiplied by Avago Joe's number, which is given by the symbol and a however gotchas number constant that we should remember is 6.2 to times 10 to the power of 23 and it's in units off per moles. That's how the moles can cancel up. Okay, so the 1st 1 b have here is aluminum and, uh, aluminum. We have five grams of aluminum. So to find me the moles, we take the mass five and we divided by the molar mass. And that gives us A fee quickly is your calculator was your 0.18 months, so it's very straightforward. So then, to find the Adams number of atoms, you take this malls season. This amount of moles multiplied by. Have a God Joe's constant over here, and that will give us 1.1 times tend to the 23 but it's not running times 10 to the 23 I was going to write T E 23 and e means times tend to the exponents off, whatever the number is. Let's just call that number N E meets. Okay, so Mexico, we have his iron here, we have moles. So the fine mass, We just won't supply the moles by the molar mass. And it just wants by these two numbers that will give us 0.14 And to find number Adams. We take the number of moles multiplied by avocados number, and we get 1.5 times 10 to the 21 or e 21. These air both quite large numbers, but again, it's number of atoms in like a reasonable number in a reasonable mass. But we can see, so it's quite a lot next we have copper copper element. So here we've been given the number of atoms. So it's over here tough. See how we can isolate firm rules. So if you multiply by RV divide by, um, and A on both sides, we can get that and equals Adams Adams over of a Badger's Constant and a uh huh. Now, with this rearrangement, we can solve for moles. So we just take number Adams 2.6 times 10 to 24 divided by avocados Constant. If we do that, we get 4.37 our room, 4.317 just a 4.32 and then to get mass. We just won't supply the number of moles by molar mass get changed in 74. Just quite a lot. Suddenly, for next We have magnesium and we have this mass 0.25 to find malls. We take the mass and we divided by the molar mass in this bottom call over here or wrote over here. And so 0.2 via divided by 24.3, will give us 1.3 to the times 10 to the power of I get a four or just being leg before identify number Adams. We just multiply the moles by afterguard Joe's number and we are out my little large number 6.19 I went to to the power of or E to the 19. This is an E. Next we have sodium and a so we have malls. Let's find the mass. So masses. Most times moments just multiplied this figure by this figure, and we get 0.62 mm. And to find the number Adams, we just take moles and multiply it by more. The average Rogers constant right over here. That population gives us 1.6 times 10 to the 21 or e to the 21 boss, but at least we have uranium. So in, well, this just like 10,000 Adams to find number of moles, we have to use this rearrangement and his number. Adams, divided by other goggles constant and that will give us a very small number. 1.6 times tend to the native 20. So that is quite it's on a negative number, but just an extremely small number. And lastly, to find the mass we just multiply moles by molar Mass, and that will give us 3.9 times 10 to the negative 18 or e to the negative 18 again, not a negative number, because we can't have a good of mass, but just a extremely small number. McMaster University

#### Topics

Composition

##### Top Chemistry 101 Educators   ##### Jake R.

University of Toronto