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Problem 120 Hard Difficulty

Calculate the percent by mass of the element mentioned first in the formulas for each of the following compounds.
a. iron(II) sulfate
b. silver (I) oxide
c. strontium chloride
d. vinyl acetate, $\mathrm{C}_{4} \mathrm{H}_{6} \mathrm{O}_{2}$
e. methanol, $\mathrm{CH}_{3} \mathrm{OH}$
f. aluminum oxide
g. potassium chlorite
h. potassium chloride

Answer

A.36.76$\%$
B.93.10$\%$
C.55.27$\%$
D.55.80$\%$
E.37.48$\%$
F.52.92$\%$
G.36.70$\%$
H.52.44$\%$

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Stephanie C.

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Video Transcript

all right. So here we have eight elements and we are tasked to find mass percent of the first element that each compound. All right, so it's, um, recalled the mass percent formula. It's simply the mass off the element divided by the mass of one mole of the whole compound, right? Okay. And calculation for a mass you remember is most multiplied by molar mass. Great. So here we don't have any information other than the chemical formula. That's all we need, because we know that there's one more of compound and we know molar mass of each element by using our pr the table. So let's first start off with iron to sulfate its first off by listing out each element and their masses. Okay, So if we have one more off iron to sell state, that means we have one rule of iron. One more will suffer. And for moles of oxygen, I don't want just multiply animals by the molar mass of each element. So iron mask is 55.845 grams per mole. Salford is 32 grams per mole, an oxygen 16 grumps from all all approximately. Okay, then we sum up all of these masses to get the mass total. All right? No. To find mass percent of iron. Well, simply take it's it's mass. It's individual Mass 55 and then divided by the total mass 1 51 0.9 with whom? And then we get the mass percent to be 36 0.76%. Okay, so this is the method will use Teoh. Do the rest. Next up, we have silver oxide. So first up, listing out each element seconds up, you getting down the mass of each element. So we take malls and then multiply it by the molar mass. So this is the molar mass for silver, 107.8 and more. Master oxygen is just the 16 grams per mole. Okay? Fleeced some about yet to 31 approximately so that this guy's mass percent silver is then this mass. It's amazing. It's circle it this month, divided by the total mass, which then gives us 93% just quite high. Okay, next up, we have strong team Corot Strong team is a group to muddle. If you were wondering, Come So we list out each medal or each Adam. Sorry. Could do the mass calculation. One moon for Shaunti in two moles for quarrying present in one more of strutting planet. The compound came so then we'll just multiply by Moeller Mass Mm. Once we sum this up, this is what we get. Men trying make a bit more clean. Strong teams, mass percent. It's just this massive. The element over a mask total to give us 55%. Next up, we have final Aston Tate or C four h sits 02 So just list out each album, get down the number of moles of each, and then just multiply it. But mullah Mass. Right? And And I want three some of this school you get the total mass. Okay. And no massive carbon in particular is just this 48/86 to give us again. 55.8%. All right. Next we have methanol ch 30 h. So we have to be a little careful here with the number of moles of hydrogen. So we know it's one for a carpet, um, one for oxygen, but for 100. We do have the ad each time Haijun appears. So it's 43 plus one, for I will just again multiplied by each of their moment masses, no grams per mole and then we go 52 as a total mounts. And now the mass percent for Herb in our first owned. That's just 12/52 to give us 37 0.5%. So five All right, Next up, we have aluminum oxide. So we list out each element, get down the number of moles and then multiply moles button with the mouse to find muss. And then we sum up each of these masses together to get told mass. Sorry, this sums up to 100 and to also he'll be caught it just tricking, chucking you. But, um, the mass for methanol of 32 not 52. But I'll tell you makes Merson's. But this is like 1/3 12 or 32 someone went to 1/3. Okay, so now the mass percent off aluminum would be to times of it over when 02 to give us 52.9%. Next up, we have potassium chlorate, so we have to be careful here. This is eight like one oxidation state less than Chlor eight playoff Cielo to still, it's he'll be caught at. So we're still going to list out each element in our little table here and get down the mess so no one will hear one. Well, there for chlorine and to muscle oxygen this time. Right? So now we put down the molar mass. We know molds multiplied by molar. Mass is mass 35 small for chlorine and 16 grams wall for oxygen. And this all sum's to be 106 point size. Okay, No more mass for the mass percent for potassium is 39/1. 06 That gives us 36.7% of potassium quarry. Claw right is with us. Lastly, we have this salt over here protesting chloride. Okay, so, just like usual will list out each moment and it's one moles each more. One move here sold rece heartiest in the mass 39 grams, one more multiplied by the molar. Mass itches. You know, it's gonna be the mole amounts value, but this is not a mass. Hey, we add those two masses together and we get 74 0.5 grams. Okay, then the mass percent for potassium is 39/74 0.5, just 52.4%

McMaster University
Top Chemistry 101 Educators
Stephanie C.

University of Central Florida

Nadia L.

Rice University

KS
Karli S.

Numerade Educator

Jake R.

University of Toronto