Question: how many moles of carbon are in 13.0 g of ibuprofen?
Answer: In each mole of ibuprofen there are 13 atoms of carbon. Multiply 0.0791 moles by 13 atoms C/mol to get the number of carbon atoms. There are about 1.03 atoms of C. Use Avogadro's number to find the number of moles (there are 6.022 x 10^23 atoms/mole) of carbon.