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### Calculate the percentage by mass of oxygen in the…

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Problem 24

Determine the formula weights of each of the following compounds: (a) nittrous oxide, $\mathrm{N}_{2} \mathrm{O}$ , known as laughing gas and used as an anesthetic in dentistry; (b) benzoic acid; $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{COOH}$ a substance used as a food preservative; $(c) \mathrm{Mg}(\mathrm{OH})_{2},$ the active ingredient in milk of magnesia; (d) urea, $\left(\mathrm{NH}_{2}\right)_{2} \mathrm{CO},$ a compound used as a nitrogen fertilizer; (e) isopentyl acetate, $\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{C}_{5} \mathrm{H}_{11},$ responsible for the odor of bananas.

a) 44.01 $\mathrm{amu}$
b) 122.1 $\mathrm{amn}$
c) 58.3 $\mathrm{aml}$
d) 60.1 $\mathrm{amm}$
e) 130.2 $\mathrm{amm}$

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## Video Transcript

I think this problem We have to find out the forming a weight of some of the compounds the first we have into. So the formula wayto compound is simply the addition off the formula wears the atomic wears off each Adam present in the compound. So here we have two night rose and that means we have to tow No, that would make mass off nitrogen, which is fourteen point Sirus six seven atomic mass unit. And since we have two nitrous and we have to multiply, it is by two last the at a banquet of oxygen, which is sixteen point zero am you? And since we have only one oxy and we don't need to multiply it for anything and this will give us a head off forty four point zero one and I'm assuming it. And this is the formula myself into If you go to the second one here we have him H c seven h five o two. So here. Ah, we have seven carbon and carbons. Catterick masses to a fund zero one Ammu. And since we have seven carbon multiplied by seven, then we have five plus one. Six had risen. I'd risen settlement weight is one point Oh, eight a mu times eight out. I'm sick. Says you him six had risen and then we have oxygen. Just sixteen burnt Ciro times two or cleanly ham. So that total will give us a bell off one twenty two point oneto emu And this is them. Formal amounts of this compound nine turn one. We have m Jewish too. And so the atomic weight of ignition is twenty four point three zero and the multiply. And since we have only one mag nation, we don't need to mentor paid anything and then we have to oak season. That means sixteen point all for our season. I'm struck schism, and we have one high treason. Want land or eight times two said he'd give us a value of fifty eight point Streeto Ammu. So this is the formula mus for dis compound. Then we have in each two to seal. So you have to knight prison segments on right prisons from romances fourteen point zero six seven times two. Then we have four high treason. Minutemen's one point or eight names is for, and then we have carbon to a plant zero on serious seven times. Oh no, it's only one carbon. So we don't need two. Multiplied many thing and finally have one oxygen sixteen point zero. So the total is fifty point zero five six a mule. So this is the formal emus for this compound. And then finally we have see three sotto si five h eleven. So we have seven carbon in total. You're a pansy, Ron. Is them entering must of carbon game seven. Plus we have eleven plus three total fourteen high treason one point zero zero eight. But I was fourteen. Bless you standpoint, Syria, which is the more elements off the adequate off oxygen and we have two excision. So this will give us a value off one thirty point one eight and to make Masumi and this is the formula mus for this compound.