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# Moles chemistry question watch

1. Admittedly even at A-level I'm still a little shaky on the definition of a mole. I understand that a mole of a substance contains 6.02 x 10^23 grams, but with that knowledge I can't seem to get the right answer to this question:

What is the number of atoms in 2.8 grams of ethene?
Data given: Molar mass of C2H4 is 28g mol-1, Avogadro constant is 6.0 x 10^23

My working is:

28 g of ethene = 6.0 x 10^23 atoms
therefore 2.8g of ethene = 6.0 x10^22 atoms

The correct answer is 3.6 x 10^23 grams. I know that there are 6 atoms in an ethene molecule but how do I use that to arrive at the correct answer? Does one mole of ethene not contain 6.0 x10^23 atoms?

Thanks
2. As you said, there are 6 atoms in an ethene molecule, so you have to alter your answer to fit. You were on the right lines, so you just need to do the last step. An atom refers to the smallest particle of a chemical ELEMENT that can exist.
3. (Original post by Gabzinc)
Admittedly even at A-level I'm still a little shaky on the definition of a mole. I understand that a mole of a substance contains 6.02 x 10^23 grams, but with that knowledge I can't seem to get the right answer to this question:

What is the number of atoms in 2.8 grams of ethene?
Data given: Molar mass of C2H4 is 28g mol-1, Avogadro constant is 6.0 x 10^23

My working is:

28 g of ethene = 6.0 x 10^23 atoms
therefore 2.8g of ethene = 6.0 x10^22 atoms

The correct answer is 3.6 x 10^23 grams. I know that there are 6 atoms in an ethene molecule but how do I use that to arrive at the correct answer? Does one mole of ethene not contain 6.0 x10^23 atoms?

Thanks
One mole of ethene contains 6.0x10^23 molecules, not atoms. So 2.8g is 0.1 moles or 6.0x10^22 molecules. Then multiply that by 6 because there are 6 atoms in an ethene molecule.
4. (Original post by TheMindGarage)
One mole of ethene contains 6.0x10^23 molecules, not atoms. So 2.8g is 0.1 moles or 6.0x10^22 molecules. Then multiply that by 6 because there are 6 atoms in an ethene molecule.
Oooh!
OoOoOoOh i see now, thanks!

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