## Finding the molecular formula [ENDORSED]

Nahelly Alfaro-2C
Posts: 59
Joined: Wed Nov 15, 2017 3:04 am

### Finding the molecular formula

After finding the empirical formula of a molecule, would you use the molar mass of the empirical formula to find the molecular formula of a molecule?

Odalys Cuevas 1C
Posts: 31
Joined: Fri Apr 06, 2018 11:02 am

### Re: Finding the molecular formula  [ENDORSED]

To find the molecular formula, you would need the molar mass of the empirical formula and most likely the molar mass of the molecular formula will be given. So all you do is divide the molar mass of the molecular formula by the molar mass of the empirical formula and you will get your answer needed to multiply the empirical formula to get the molecular formula. Hope that makes sense.

Or Fisher 1I
Posts: 35
Joined: Fri Feb 02, 2018 3:00 am

### Re: Finding the molecular formula

An example of this is if you have an empirical formula CH2O. The molar mass for this would be 12.011+(1.008*2)+15.99=30.017 gmol-1. If it told you that the molar mass of the molecule you are trying to find, in this case Glucose is 180.102 gmol-1, than you would divide 180.102 gmol-1 by 30.017, and you would find that it is equal to 6. You would then multiply CH2O by 6 to get C6H12O6, which is the molecular formula of glucose.

Sarah Brecher 1I
Posts: 31
Joined: Fri Apr 06, 2018 11:02 am

### Re: Finding the molecular formula

Additionally, sometimes the empirical formula is the same as the molecular formula. All you need to do is calculate the molar mass of the empirical formula and compare with the given molar mass stated in the question. If the two numbers are the same, then your molecular formula is your empirical formula.

Posts: 27
Joined: Fri Apr 06, 2018 11:04 am

### Re: Finding the molecular formula

If the molar masses for both the empirical and molecular formula are the same, does this conclude with being able to find the molecular formula from the start of the problem, bypassing calculations for the empirical formula?

Chem_Mod
Posts: 18918
Joined: Thu Aug 04, 2011 1:53 pm
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### Re: Finding the molecular formula

When you find the empirical formula and find that the molar mass of the empirical formula is the same as the molar mass of the molecule, you reach the conclusion that the empirical formula you found is the molecular formula. To reach this, you probably already employed series of steps so I am not sure what you mean you can bypass all the steps.