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Atoms to Grams and number of moles

Submitted by Anonymous on 24 July 2005 - 5:26pm.

Hi, how do you calculate the number of atoms present in 6.00g of Oxygen gas?

Also, calculate the number of moles present in 14.02 Nitrogen gas.

Thanks

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Submitted by Anonymous on 24 July 2005 - 7:46pm.

divide the mass by the molar mass to get the moles (n=m/M)
multiply the moles by Avrogadro's number to get the number of atoms.

e.g. nitrogen gas is N2, molar mass of N2: M = 2*14 = 28
14 is the atomic mass of N in amu (and the molar mass of N in g) you find it on your periodic table

n = m/M = 14g / (28g/mol) = .5mol
(a little bit different if you type in all the digits)

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Submitted by Anonymous on 25 July 2005 - 7:32am.

Just to clarify that last post; n=m/M

n = number of moles
m = mass
M = Relative Molecular Mass (RMM), aka Molar Mass or Relative Atomic Mass

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