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Problem 117 Hard Difficulty

Calculate the number of moles of hydrogen atoms present in each of the following samples.
a. 2.71 g of ammonia
b. 0.824 mole of water
c. 6.25 $\mathrm{mg}$ of sulfuric acid
d. 451 g of ammonium carbonate

Answer

a. 0.477 $\mathrm{mol} \mathrm{H}$
b. 1.648 $\mathrm{mol} \mathrm{H}$ atoms
c. $=0.127 \times 10^{-3} \mathrm{mol} \mathrm{H}$ atoms
d. 37.5 $\mathrm{mol} \mathrm{H}$ atoms

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Video Transcript

So here we have four compounds. Origins have been a bit different. We're finding the malls of hydrogen Adams in particular, right? Uh so in order to do that, we will first find the moles of the whole compound which we know. The formula for moles is mass over Mullah mus and will be mess of the whole compound divided by the molar mass of the entire capo. Right? So now, in order to take moles of the whole compound, two moles of the multiplier gin need to understand, Like how this thes molar ratios work. So we know about just by Lippman, we have ammonia. Sure. One more of ammonia who always have one mole of nitrogen for every three moles of hydrogen. So, like a 1,000,000 turner stand what these sub scripts here means, So they are basically molar ratios of each other. So one mole of ammonia, one mole of nitrogen, three moles, a hydrogen. Yeah, I hope that makes sense. So that's basically what we're gonna do to self all of these questions of it. So here, ammonia, two points over one grams of ammonia. Find by the molar amounts of ammonia which found to be 17 grams per mole. Uh huh. Right. So that equals 0.1590 point 159 Moles of ammonia is present now, right? So to find moles of hydrogen, what we basically are going to do know when he used another color is multiplied. Total malls. Well, you guessed it, three Because Reverend al Ammonia, we have three extra moles of hydrogen just because of the subscript here. Right? So then this multiplied by three gives us zero point 477 moles of hydrogen. You know, it's interesting. I'm a bit counterintuitive that we would have more moles off. Hi, Jim, then of ammonia. But do you really understood what I just said? Look, a minute ago. It makes sense because there are more moles of hydrogen than there are Adams, R. Adams, compounds of ammonia. So I'm feeling and there are more moles of hydrogen atoms than there are of ammonia molecules because there's there's three times more. Okay, I think it makes sense now. Okay, now we're moving on toe water, so he has your 0.8 to 4 moles off water. We will divide, but we will divide that by the molar. mass of water whim and actually rounded with moments of water because we already have the moles of water. So we have 0.8 to 4 molds of water. So then, how many moles are you? Do we have? Well, if you remember what I did, just above we have priced. We'll have places, many malls. Because that's what the super sub script don't. There means claims to to give us, um, which is double of that, which is one 0.648 Right, Because for every more of water, we have twice as many moles, hydrogen and the same moles of oxygen. Yeah. Next up, we have owns off your kassid. So here we have more grams. So we must do, you know of conversion, So extract up here, okay? And we want when we want Gramps. So the unit conversion ratio that we're going to use this one gram and 1000 milligrams over 1000 micrograms. We're using this because this basically is equivalent to one, and it cancels out milligrams, replaces it with Gramps. Right? So now what? We have grams people, then divide by Mullah mass of sulfuric acid to give us moves. So the molar mass of Saul uric acid, 98 point 07 mine grams per mole. Uh huh. No money. SPS. So that is equivalent to 6.3 stove in 6.37 Okay, times tend to the exponents. Negative. Five months. Right. So we will then multiply the total Mel's by two. Uh huh. To give us the moult of hydrogen, which is then one point 27 1.27 malls. No times. 10 to the exponents. Negative for moles of hydrogen. Okay. And lastly, we have ammonium carbonate. Quite a lot of it. So you will take this mass divided by the molar mass of money in carbonate, which is 96 needs grams per mole, which gives us total more of four points. 69 Okay. Now, to find the moles of hydrogen, we will now multiply Hormel's by notches for for multiple buy to eight. Uh huh. Which is equivalent to 37 0.5 seven months. Right

McMaster University
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