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Gatorade

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I hope this thread is in the right section. Anyways, I decided to make this thread because I know a lot of people struggle with homework problems (including myself) and decided to make a place where someone can post the question that they are stuck on and someone will help them out and explain it to them.

An easy way to understand your homework better, and an easy way to earn Rep Points if you help someone.

Hopefully people will actually use it, I think it's a good idea.
 

Vossler

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I think Ziz made a thread on Homework but it had a diffrent point to it.
 

Vossler

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Whatever it dosen't matter lets get back to disscusing homework.
 

Takuya

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*takes off his [imaginary] glasses* Only to help you understand, not to tell the answers. But there's no guarantee for quality; we're not teachers, you know. Then again there was that notice in the register page, I remember, that noted (essentialy): "The site (KHInsider) was not established for educational purposes."

The problem of integrity is also troublesome. Do we take responsibility in your success in school? Was your school intended to be the your method for learning? It's sort of like cheating, as twohearts mentioned.
 

very differentiable
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I'm willing to help, starting next week that is. I've got to finish something for graduation this week.
 

Gatorade

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I don't believe that it would be cheating. As Takuya said, it is simply helping people understand what to do.

You guys don't have any homework? What about studying for midterms? I have a question from my Chemisty Midterm Review Packet...

A compound contains three elements carbon, hydrogen, and oxygen. Combustion of a 10.0 g sample of that compound gives 19.10 g of CO2 and 11.74 g of H2O. Calculate the masses of C, H, and O in a 10.0 g sample assuming all the carbon is converted to carbon dioxide and all the hydrogen is converted to water.

What the hell do I do here?
 

very differentiable
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Write down how the reaction goes, convert from grams to moles and then look at the ratio (both before and after reaction). This should give you the amount you have of each material after the reaction.
 

violent_anger

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that shit is easy. all you need to know is that you have unlimited O2 from the air, and a small amount in the compound. from 19.10 g of CO2 and 11.74 g of H2O, you need to find out the mass of C and H respectively. add them together, then subtract that number from the 10g, and that'll give you the mass of O in the compound.


I guess you could convert to moles or something
 

Gatorade

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that shit is easy. all you need to know is that you have unlimited O2 from the air, and a small amount in the compound. from 19.10 g of CO2 and 11.74 g of H2O, you need to find out the mass of C and H respectively. add them together, then subtract that number from the 10g, and that'll give you the mass of O in the compound.


I guess you could convert to moles or something
Yes, but the thing I can't do is find out the masses of C and H.

Write down how the reaction goes, convert from grams to moles and then look at the ratio (both before and after reaction). This should give you the amount you have of each material after the reaction.
Convert which things to moles? I'm still very confused, sorry.
 

very differentiable
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All right, you need a periodic table for this. A mole is an amount of mass like grams. A mole contains the exact amount of atoms (always the same) so you will get exactly the amount of grams as the mass of one atom is expressed in U. A proton and neutron are about one U each. So if we would take one mole of atoms containing one proton and one neutron, it would weigh about two grams. In the periodic table you can look up (relative) atomic mass. Take that mass, put the word gram behind it instead of U and that is exactly how much mass one mole contains.To go from grams to moles, take the mass of the material and divide it by the mass of one mole.
 

Gatorade

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All right, you need a periodic table for this. A mole is an amount of mass like grams. A mole contains the exact amount of atoms (always the same) so you will get exactly the amount of grams as the mass of one atom is expressed in U. A proton and neutron are about one U each. So if we would take one mole of atoms containing one proton and one neutron, it would weigh about two grams. In the periodic table you can look up (relative) atomic mass. Take that mass, put the word gram behind it instead of U and that is exactly how much mass one mole contains.To go from grams to moles, take the mass of the material and divide it by the mass of one mole.
Ok thank you that makes complete sense. Along with that, I did eventually find my notes on it and I think I get it. For anyone who did this problem, would the masses be:
C- .1919 g
H- 1.52 g
O- 8.29 g

These numbers seem a little off to me, but I think I did it right.

Thanks for your help guys.
 
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very differentiable
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From the top of my head, the answer is probably right, and it's pretty close even with a calculating error.
 

Gatorade

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From the top of my head, the answer is probably right, and it's pretty close even with a calculating error.
Alright well thanks so much. I'm going to give you rep, but it says I've given out too much in the past 24 hours. So if you don't recieve any soon, then remind me and I'll be sure to give you some.

You too violent anger

Anyone else with any questions? I may be back with some more later.
 

violent_anger

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There is no way that's right.

1 mole of O has a mass of 16g, and 1 mole of C has a mass of 12g. so 1 mole of CO2 would have a mass of 44G. To find the mass of C in CO2, multiply it by 12/44. 19.10 g of CO2 X 12/44 would be about 5.209 g of C.

Mass of H is about 1.304, if you do the same thing.
 

Gatorade

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There is no way that's right.

1 mole of O has a mass of 16g, and 1 mole of C has a mass of 12g. so 1 mole of CO2 would have a mass of 44G. To find the mass of C in CO2, multiply it by 12/44. 19.10 g of CO2 X 12/44 would be about 5.209 g of C.

Mass of H is about 1.304, if you do the same thing.
Ahhh ok I know exactly what I did wrong. You are completely correct. Thanks a lot.

Does this make the emperical formula C3H5O2??
 
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