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Problem 118 Hard Difficulty

Calculate the percent by mass of each element in the following compounds.
a. calcium phosphate
b. cadmium sulfate
c. iron(III) sulfate
d. manganese(II) chloride
e. ammonium carbonate
f. sodium hydrogen carbonate
g. carbon dioxide
h. silver(I) nitrate

Answer

A.19.97$\%$
B.53.91$\%$
C.48.01$\%$
D.56.34$\%$
E.49.95$\%$
F.14.30$\%$
G.72.71$\%$
H.68.11$\%$

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Allea C.

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Video Transcript

All right, So we have eight chemical compounds here. We're going to find the mass percent of each element in each of these compounds. Okay, So lower. Oh, formula we're gonna use to find. My percent is taking the mess of each element. So master the elements and and dividing it by the total mouse of one mole of compound right way. Always assume one more compound. All right, so you haven't given us any, like moles or mass or anything of these compounds. But we have. We already know that we're working with one mole of each compound, and we can easily calculate the molar mass. And we know the masses. A cool, true moles multiplied by more mass. All right, so let's get started. So, first off, we have calcium phosphate. You can start off by listing all the elements present here. We have a calcium boss, wrists and oxygen. Right. Well, huh. Okay, so let's first calculate the m e. The mass off each element, the massive one mole of each of the elements of it. So we're in east this formula. What it do most wants a problem with the mass. So, in one mole of calcium phosphate. We have three moles of calcium. So we missed wall supply. Three cost seems more mass, which is around 40. Right in here. In one more health seemed fall sweet week of to most of phosphorus sociales playing moles. But Muller mass 30.9 and likewise, we have eight months of oxygen. Yeah, just gonna call it 16. Mm mm. Right. So now we're going to some up these numbers. Well, sure. Then, you know, give us what our total is there. Total mass. Just 300 in 10 0.18 All right, So the number of getting tears, if I were they have included more sick fix, like, written here. But you don't have so much time for me to be waiting. All these effects. You have eight questions of these to go. So now what we're gonna do to find love percent of each element is we're going to take this number and divided by the total over here. Very well. Okay, so this column is the mass percent. So three times 40 is 1 20 1 20 divided by three turn. Basically, these equivalent took 38 point 8% right? Okay, so that's what. We're gonna do it for casting now. Same thing prospers. We take this mass invited by the M total, which will give us 19.9%. Huh? 19.9%. Oh, and for oxygen will also apply this mass divided by the total. Actually, it was 41 0.3%. Mm. That's how old for the remaining. Okay, we go over it one more time how this is working, Cagney and each will just list down each element, right? There's gonna be in addition that we're about to do and we use this formula here, take moles element and multiply with more massive element. Assuming one mole of copper from one mole of compound, we have one mall of cadmium cad names molar masses 112 point for 11 We have one more sulfur and sulfur. Small amasses 32 0.66 and we have formals of oxygen. My oxygen small amasses 15.99 mine four or trance to 16. If we send this up, including all the sig figs or more digits. We had 208 0.47 And this is the mass total number is gonna take each of these masses and divided by the mass total to find mass percent. Oh, mass percent is gonna be in this column myself happened then. Okay, Quick, Right. So 1 21 are all sorry. 112 divided by 208 equals 53 0.9%. That's a five next herself for 32 over. Change in eight will give us 15 0.4% and lastly for oxygen for multiplied by 16 then divided by tension eight will give us 30 0.7%. Okay, now that we have my understanding of how this works again, it'll move a bit faster. Next up, we have iron three saw feet. You just quickly list out each element. Now calculate the masses really way Have two moles higher irons. Molar Mass. 55. Don't forget, we need to multiple a Who's through this bracket. So there's three moles of software. Saul. First Momus is pretty too. And theory of 12 moles of oxygen, oxygen swollen round of 16. Right, So if we add this up to find the mass total me, uh, 399 0.88 tell him So now they would be quite easy for us to calculate mass percent who just takes massive. The element divided by mass of the whole compound. It's gonna list out the answers I got here. 27.930 wait for iron, 24 0.0, 567 for sulphur in 48. Present Oxygen. Okay, next up, we have magnesium chloride. I believe I need him to chloride. Okay, first up, list out. Um, compounds make a little chart. Okay, now let's calculates, amasses moves all the play by molar mass One mall of magnesium, our man Guineas. Sorry. Multiply it by a small amounts to moles off chlorine multiply, but it's molar mass on 35. Sum that up to give us the mass total of this compound No easily calculate mass percent. So we take massive the element and drive by mass total week or get approximately 43 0.7% for chlorine. We'll get 56 0.3%. All right, Next up, we have ammonium carbonate, my in carbonate. So we're just good as above list upped. Well, was each opponent just a long, well straight line, but no time like late Mass. So two moles late region multiplied by its small amounts. Eight months of hydrogen and it's more losses one. So we eat, multiply by one. Um, one more of carbon. And it's four months was 12.10 dozen. In here, we have three moles of oxygen. Sum this up to find the mass tall 96 point on mine. Do what we can when mass percent. Okay. Simply by taking massive element of mass total. Um, Okay, nitrogen, we got 29% hydrogen, 8.4% groups. Carbon 12 points. Life person and oxygen compound 49.95% oxygen. Your pride. Okay, next up. Sodium bicarbonate or sodium hydrogen carbonate, which I believe is like baking soda. Okay, so we're gonna list out Oh, for these elements, then step to cut early mass live each moment. So just most multiplied by moment. Mass. So more mass of sodium strain, 2.9. Okay, Mama's hard region is one B of one mole, one times, one carbon. We have one more carbons. That's just gonna be 12. Here we have three moles of oxygen. Okay, let's add this up to find the total Mass 84. Oh, now, um, define mass percent. We just Same as above. We take B A massive the element and then divide by mass total. These are the numbers that I'm getting king from the outside Sub one list healthy elements Step two. Calculate mass of each element one times the moments of of carbon 12 is just 12 to most off oxygen king. And this and a 44 it would be step three tech yoli or some up must total. No, sir, for speculate mass percent. Uh, to these were the numbers I'm getting 27 for Ah, carbon and 23 for oxygen. Last one is still run. A tree came not much as they hear it. Seimas the whole seven that were above king from all silver So there's the molar mass Wimal off nature gin. This is a smaller mass three moles of oxygen. And here's a smaller mass and the sum total 158 finally mass percent massive. The moment over mass total. I just can't give us 60% silver, 8.8% nitrogen, 30 percent Mary by 3% oxygen. Okay,

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Top Chemistry 101 Educators
Allea C.

University of Maryland - University College

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JH
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