Problem: Ibuprofen has the following mass percent composition:C 75.69%, H 8.80%, O 15.51%.What is the empirical formula of ibuprofen?

FREE Expert Solution

We’re being asked to determine the empirical formula of a compound composed of C, H, and O, given C 75.69%, H 8.80%, O 15.51%.



Recall that mass percent is given by:


% mass=mass of Xtotal mass×100


Assuming we have 100 g of the compound, this means we have 75.69 g C, 8.80 g H, and 15.51 g O.



Now, we need to get the moles of each element in the compound. 

The atomic masses are 12.01 g/mol C, 1.01 g/mol H, and 16 g/mol O.


75.69 g C×1 mol C12.01 g C =  6.30 mol C


8.80 g H×1 mol H1.01 g H =  8.71 mol H


15.51 g O×1 mol O16.00 g O =  0.97 mol O



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Problem Details

Ibuprofen has the following mass percent composition:

C 75.69%, H 8.80%, O 15.51%.

What is the empirical formula of ibuprofen?


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