# of Molecules

Science questions not covered in Chem 14A and 14B. Try to limit questions to chemistry (inorganic chemistry, physical chemistry, organic chemistry, biophysical chemistry, biochemistry, materials science, environmental chemistry).

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# of Molecules

Postby 004788646 » Fri Oct 14, 2016 5:17 am

I just want to make certain that the number of molecules in a compound can be found using the molecular formula. Could someone confirm this?

Sydmon Nguyen-Tran 1N
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Re: # of Molecules

Postby Sydmon Nguyen-Tran 1N » Fri Oct 14, 2016 12:28 pm

Yep. Because the molecular formula shows the actual number of atoms of a molecule.

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Re: # of Molecules

Postby Matthew_Vargas_2G » Sat Oct 15, 2016 12:22 pm

Yes, you would use avogadro's number in order to find it. So say you had the molecular formula C4H6, you would use the 4 mols of carbon x 6.022x10^23 molecules/mol which would give you the number of molecules.

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Re: # of Molecules

Postby Amy_Bugwadia_3I » Sat Oct 15, 2016 7:12 pm

Like the other posters mentioned, in order to find the number of molecules in a compound, you would need to use Avogadro's number. If you're given the amount of the compound in grams and you want to find how many molecules of that compound there are, convert grams to moles, and then go from moles to molecules using the conversion factor 6.022 x 10^23 molecules for every 1 mole.

If you're given the molecular formula, you can find out the number of atoms of a particular element as follows: If the molecular formula you're given is H2O, you know that for every 1 mol of H2O, there are 2 moles of H+. For every 1 mole of H+, there are 6.022 x 10^23 H+ atoms. Thus, you use that as a conversion factor and end up with the number of H+ atoms in the compound.

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