Finding the molecular formula  [ENDORSED]

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

Finding the molecular formula

Postby Nahelly Alfaro-2C » Sat Apr 07, 2018 9:38 pm

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]

Postby Odalys Cuevas 1C » Sat Apr 07, 2018 10:19 pm

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
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Joined: Fri Feb 02, 2018 3:00 am

Re: Finding the molecular formula

Postby Or Fisher 1I » Sun Apr 08, 2018 12:09 pm

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
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Joined: Fri Apr 06, 2018 11:02 am

Re: Finding the molecular formula

Postby Sarah Brecher 1I » Fri Apr 13, 2018 6:01 pm

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.

Anthony Mercado 1K
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Joined: Fri Apr 06, 2018 11:04 am

Re: Finding the molecular formula

Postby Anthony Mercado 1K » Sun Apr 15, 2018 5:32 pm

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
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Re: Finding the molecular formula

Postby Chem_Mod » Sun Apr 15, 2018 6:24 pm

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.


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