posted
I just realized that I am having a quiz tommorow in Chemistry. Furthermore, I understand little of the material. Thankfully, I managed to obtain several practice questions, which cover all the material on the quiz.
If anyone could please explain to me how to do these problems, the concepts behind them, I would be endlessly grateful. Also, it would be great to just be given a link to an explanation/how to do. Thank you so much!
1. A compound contains 4.02 grams of Nitrogen and 11.4 grams of Oxygen. This gas has a density of 4.82 grams/liter at STP. What is the true formula?
2. What is the % of water in NaC2H3O2*(imagine that the star is a dot -- I have no idea what that means, though)3H20
3. An snvne (huh?) contains 52.1% Carbon, 34.8% Oxygen and 13% Hydrogen. 23 grams dissolved in 250 grams of water raised the boiling point by 1.04 Centigrade. What is the true formula? (Molal boiling point elevation of water =0.52)
Also, how do you name compounds and stuff like that?
Posts: 3060 | Registered: Nov 2003
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posted
Have you been showing up to class? The fact that you don't even know what the * means leads me to believe this... I could explain all of the above problems so you could understand it. I was a professional chemistry tutor for four years, but you've got to convince me that you are worthy of the explanation. So far you haven't and it seems more like a solid case of "do your own homework".
posted
AJ, I was gonna ask that same question. Knowing how to name compounds is a pretty basic task. That said, good luck Phanto. Science is definately my weak subject, and it took me many many hours of studying. But, I ended up doing pretty well in it, so even if it seems totally incomprehensible now hang in there.
posted
I have indeed been showing up to classes; however, I have not been as good of a student reviewing the material as I should have been. You could call me overconfident, for we covered this material quite rapidly and have switched to balancing equations and all the replacement laws, which are very natural for me to do. As such, my hubris blinded me to the reality that I did not understand truly the material we had just covered.
If you feel like judging me, then do so. If you feel like helping me, it would be much appreciated.
posted
As far as I can tell, it's a typo/transcription error. I haven't figured out what it was meant to be. Posts: 32919 | Registered: Mar 2003
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Actually, the chemistry class I'm teaching this year is great! Bright, and very motivated. On their last test (on naming binary compounds), the LOWEST grade was a 95. They have a bit more trouble with the math-oriented sections. The chapter on moles is likely to yield much lower test grades.
Posts: 32919 | Registered: Mar 2003
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posted
I've never actually done any of the Chemistry that you asked, but I may be able to help with part (a) without knowledge of the chemistry
quote: A compound contains 4.02 grams of Nitrogen and 11.4 grams of Oxygen. This gas has a density of 4.82 grams/liter at STP. What is the true formula?
Density = mass/volume At STP, 1 mol of gas has a volume of 22.4L
4.82 = mass / 22.4 mass of 1 mol of this gas = 107.968 g
This has 4.02g N and 11.4g O
which means for every 1 g of N, it has 2.83g O.
so x + 2.83x = 107.968g x = 28.19 g = nitrogen 2.83x = 79.777 g = oxygen
Nitrogen is 14 (g/mol) Oxygen is 16 (g/mol)
28.19 g / (14 g/mol) = 2 mol N 79.777 g / (16 g/mol) = 5 mol O
Therefore N2O5
I have no idea if I did that right, and I have no idea how to do any of the others.
quote: Ah, moles. Just have them dissect one - that should spark their interest.
Well, I have given out these critters some years . . . but I'm not sure how dissecting one would help.
Posts: 32919 | Registered: Mar 2003
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--As a general note, the reason that I can not look these up in my textbook is because my textbook was stolen from my locker, which had a defective lock, as I have recently discovered. I have replaced it with a thick padlock which is both big and emotionally uplifting ^^.
Posts: 3060 | Registered: Nov 2003
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posted
You used a fairly straight forward approach. I am grasping one of the concepts as we speak; I understand intuitivly the math behind your procedure, but will have to formulate it verbally before I can understand.
If I can not do that, I will say so. Thanks for the help! Posts: 3060 | Registered: Nov 2003
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posted
ack, didn't get back to this yesterday. I'd planned on breaking down each problem in detail. But it looks like you got a lot of help on the right track. The biggest concept I think they are teaching other than naming is the idea to convert everything to moles. If you do that when you start generally the data starts making sense.
posted
Do y'all know the mole song? It's saved me many times since high school.
Mass over formula weight That's the way you get the mole Then divide the largest by the smallest Push the little buttons is your goal Multiply it, multiply it, multiply it till it's whole.Posts: 26077 | Registered: Mar 2000
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posted
kat, I need to know what tune that goes to!
And I just realized, I forgot to teach my students about Good Little Johnny! *smacks head* Well, that'll start class off with a bang tomorrow. Posts: 32919 | Registered: Mar 2003
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I've been out of school for two long - I can't remember how to do the first question.
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And I just realized, I forgot to teach my students about Good Little Johnny! *smacks head* Well, that'll start class off with a bang tomorrow. 
