#1
So, question is:

How many hydrogen atoms are in 3.71 pg of C24H26O7.

So first, to convert pico grams to grams, 3.71 x 10 ^ -12 g.

Then find the number of mols of H using the number above and the molar mass of H. Then find the number of atoms using the mols of H and Avagadro's constant, but I can't seem to get the right answer. I've done it several times so I don't think it's a simple calculation error. Any help?
#3
Just reading that gave me a headache. I'm glad I'm not in school anymore. Good luck.
None are more hopelessly enslaved than those who falsely believe they are free.
#4
*outstretches hands and says "this many"*
Quote by denizenz
I'll logic you right in the thyroid.

Art & Lutherie
#5
God I hated chem..good luck bro. You're gonna need to find a chemistry major to answer that one for ya.
E-married to ilikepirates

Quote by bloodtrocuted93

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#8
Quote by technicolour
So, question is:

How many hydrogen atoms are in 3.71 pg of C24H26O7.

So first, to convert pico grams to grams, 3.71 x 10 ^ -12 g.

Then find the number of mols of H using the number above and the molar mass of H. Then find the number of atoms using the mols of H and Avagadro's constant, but I can't seem to get the right answer. I've done it several times so I don't think it's a simple calculation error. Any help?


Almost, once you have the number of molecules, which is attained by multiplying your moles by Avagadro's number, multiply the number of molecules, by the number of atoms/molecule. So in hydrogen's case you would multiply number of molecules by 26.
It's just that easy.
c24h26o7
So, 3.71x10^-12 divided by the molar mass of that is... 3.71x10^-12 / 426, which gives you... 8.71x10^-15moles, take that number multiply it by avagadros number gives you... 8.71x10^-15molesx6.02x10-23...so you have 5.24x10^-37molecules. NOW times that by 26, gives you the final answer of.....


1.36x10^-35. am i right or wat.


I GIVEZ U DA ANSWA!!
Last edited by tona_107 at Sep 17, 2008,
#9
Well you gotta find the grams/mol ratio of the compound - not just the hydrogen part of it.
Quote by denizenz
I'll logic you right in the thyroid.

Art & Lutherie
#10
3.71 x 10 ^ -12 g of the substance.

Divide that by its RFM, which is 288 + 26 + 112 = 426

To give the moles. I can't do it, I don't have a calculator.

Avogadro's constant = 6.0221415 × 10^23 molecules in one mole.

So multiply the constant by the number of moles to find the number of molecules.

Then multiply the number of molecules by 26 to give number of H atoms.

I think.
#11
chubby has it i am pretty sure (chem major here)

edit: seems right, although i havent done that kind of stuff in like two years, so i may be a bit rusty. but if you wanna talk about organic functional groups and recrystallization.....
Last edited by Skierinanutshel at Sep 17, 2008,
#12
I will try to help you... but i wont do it for you....

you need to find the mols of C24H26O7 in 3.71 x 10 ^ -12 g.

Then you take that number and multiply it by 26 (because there are 26 atoms of hydrogens in 1 mol)

this will give you the number of mols of H, then find the number of atoms with avogadro's number

I havent made chemistry for long but I dont think I'm wrong

good luck!
#14
Okay, one more question. When I divide the mass by the molar mass to get the # of moles, is the molar mass going to be 1.008 (hydrogens molar mass) or 1.008x26?
#17
Damn, I was pretty good at this a couple of years ago, but not anymore, I guess, and it's in English, too, so I can't quite help you But chem is fun, you can make some awesome stuff like acid
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#18
Quote by technicolour
Okay, one more question. When I divide the mass by the molar mass to get the # of moles, is the molar mass going to be 1.008 (hydrogens molar mass) or 1.008x26?


For molar mass you have to do this
MMC=24atoms x 12mu = 288
MMH=26atoms x 1mu = 26
MMO=7atoms x 16mu= 112

Then you add them all togetha.

MMC(288) + MMH(26) + MMO(112) = 426!

YAY!

Quote by technicolour
So, question is: How many hydrogen atoms are in 3.71 pg of C24H26O7. So first, to convert pico grams to grams, 3.71 x 10 ^ -12 g. Then find the number of mols of H using the number above and the molar mass of H. Then find the number of atoms using the mols of H and Avagadro's constant, but I can't seem to get the right answer. I've done it several times so I don't think it's a simple calculation error. Any help?
Almost, once you have the number of molecules, which is attained by multiplying your moles by Avagadro's number, multiply the number of molecules, by the number of atoms/molecule. So in hydrogen's case you would multiply number of molecules by 26. It's just that easy. c24h26o7 So, 3.71x10^-12 divided by the molar mass of that is... 3.71x10^-12 / 426, which gives you... 8.71x10^-15moles, take that number multiply it by avagadros number gives you... 8.71x10^-15molesx6.02x10-23...so you have 5.24x10^-37molecules. NOW times that by 26, gives you the final answer of..... 1.36x10^-35. am i right or wat. I GIVEZ U DA ANSWA!!


i'm right, right?
Last edited by tona_107 at Sep 17, 2008,
#20
Quote by Gakusey
Damn, I was pretty good at this a couple of years ago, but not anymore, I guess, and it's in English, too, so I can't quite help you But chem is fun, you can make some awesome stuff like acid


good sir, acid is the least of the things you can make...
#21
Quote by technicolour
Okay, one more question. When I divide the mass by the molar mass to get the # of moles, is the molar mass going to be 1.008 (hydrogens molar mass) or 1.008x26?

When are you going to be dividing by the molar mass of hydrogen? I'm pretty sure you have that confused with dividing by the molar mass of the original substance (some type of sugar?) but take everything I say with a grain of salt though.
#22
Well I came up with 1.36x10^11 Hydrogen atoms.

You know that the RMM of the molecule is 426.

You need to know what percentage of that mass is made up of Hydrogen atoms.

So you have 26 Hydrogens with individual RAMs of 1 so you have an RMM for Hydrogen of 26.

26/426 = 6.10% (rounded).

The mass therefore is 6.1% of 3.71x10^-12g which comes out to:

2.2631x10^-13g

Multiply this by 6.023x10^23 (avogadros constant) and you get:

1.36x10^11 Hydrogen atoms.
Sat in a lab, curing diseases. They actually LET me play with chemicals!