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Faster Method to Calculate the Molecular Formula

Posted: Sat Oct 07, 2017 1:54 pm
by Hena Sihota 1L
When asked to calculate the molecular formula of a compound (for this example: Compound C which is comprised of the elements A and B) and you're given the grams of C produced, the molar mass of C, the grams of A, and the grams of B, is there a faster way to calculate the molecular formula of C other than following this process: calculate mass % composition of A and B->convert % to grams->convert grams to moles->calculate the empirical formula->calculate the molecular formula?

Re: Faster Method to Calculate the Molecular Formula

Posted: Sat Oct 07, 2017 2:54 pm
by Michael Koger 3K
There is indeed another way to calculate the molecular formula, but the speed of this method vs. the traditional method depends a lot on the person. This is how it goes:

Step 1: By using the mass percentages and molar mass given, calculate the number of grams of each element in a mole of the substance.

Step 2: Using the masses calculated in Step 1, calculate the number of moles of each element in a mole of the substance.

Step 3: The numbers calculated in Step 2 serve as the subscripts for the elements in the molecular formula.

I hope this helps!

Re: Faster Method to Calculate the Molecular Formula  [ENDORSED]

Posted: Sat Oct 07, 2017 7:03 pm
by Chem_Mod
This is no general technique that will let you find the molecular formula faster than the technique learned in class or as described in the comment above. These problems are just long in general, but practicing them will increase your speed with solving them.