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### chemical formula

Posted: Sun Apr 15, 2018 9:33 pm
When writing a chemical formula/ equation, what is the difference between the placement of where the number goes? ... example: 2Na and Na2? I was very confused about this during quiz 1.

### Re: chemical formula  [ENDORSED]

Posted: Sun Apr 15, 2018 9:40 pm
I believe the 2 in 2Na is acting as a coefficient, so you would have 2 mols of Na whereas Na2 would change the structure of the atom. Na2 would be 2 Na bonded together while 2Na is still an unbound Na but in with a stochiometric coefficient so the ratios allow the chemical reaction to be balanced.

### Re: chemical formula

Posted: Sun Apr 15, 2018 9:42 pm
Hello!
So the placement matters when you start to have more than one element in the compound, so for H20 for example. This means there are 2 hydrogen atoms and one oxygen where if it was 2HO then it would be 2 hydrogen and 2 oxygen atoms. Hope that helps!

### Re: chemical formula

Posted: Sun Apr 15, 2018 9:51 pm
Kara Justeson 1B wrote:I believe the 2 in 2Na is acting as a coefficient, so you would have 2 mols of Na whereas Na2 would change the structure of the atom. Na2 would be 2 Na bonded together while 2Na is still an unbound Na but in with a stochiometric coefficient so the ratios allow the chemical reaction to be balanced.

-This response was very helpful! Regarding the question from the quiz... By looking at the molecules, how do we write the empirical and molecular formula? I understand that the empirical formula solely shows the "relative" number of atoms, whereas the molecular formula shows the "actual" number of atoms, but how do we find this only using the molecular structure?

### Re: chemical formula

Posted: Sun Apr 15, 2018 10:02 pm
For the molecular and empirical formulas, if you only had the molecular structure (i think you're talking about the 3d pictures with different colors representing different atoms), you could count the number of each type of atom represented and use that to directly write the molecular formula (one circle would represent one atom). Then if your molecular formula could be reduced by a ratio, you would reduce it to find the empirical formula, but if the molecular formula can't be reduced, then it would be the same as the empirical formula. Hope that makes sense and helps!