Hello! This question relates to mole fractions, though I believe you could also solve it using mass percent. Ibuprofen, C13H18O2, contains 13 moles of carbon for every total mole of the compound. Thus, we will begin by calculating the molar mass of ibuprofen as a whole, assuming it is not given.
- To calculate ibuprofen's molar mass, use 12.01 g/mol for C, 1.008 g/mol for H, and 16.00 g/mol for O. These values should be given on your periodic table. (12.01*13)+(1.008*18)+(16.00*2)=206.2 g/mol if you round sig figs correctly. This is the molar mass of ibuprofen.
- Now, divide 12.78g by 206.2g/mol (ibuprofen's molar mass). You should get 0.06198 mol. That's how many mols of ibuprofen you have.
- Now, since there are 13 mols of carbon per mol ibuprofen, multiply 0.06198 by 13. This results in 0.8057 mol carbon. To find grams, simply multiply this quantity by carbon's molar mass (12.01g/mol). You should get 9.676 g carbon.
- I hope this helped! Please note that the molar masses I used are rounded to the hundredth place-yours in class may be rounded more or less, resulting in a slightly different answer (ibuprofen's actual molar mass is closer to 206.3g/mol). Fellow tutors, please let me know if you spot any mathematical or conceptual errors on my part.
