Final answer:
The empirical formula of penicillin can be calculated by converting the given percentage composition to moles, dividing by the smallest number of moles to get a ratio, and rounding to the nearest whole number. The correct formula given the percentages is C16H18N2SO4 (Option A).
Step-by-step explanation:
To calculate the empirical formula of penicillin, given its percent composition, we convert the percentages to masses, assume a 100g sample (which makes percentages and grams equivalent), and then convert these masses to moles by using the atomic masses of each element (carbon, hydrogen, nitrogen, sulphur, and oxygen). After obtaining the moles, we divide all by the smallest number of moles to obtain the smallest whole number ratio for each element, which would be the empirical formula. Since oxygen was not given a specific percentage, we consider it as the 'remainder' to total 100%.
We can do an example computation for carbon:
- 57.49g C × (1 mole C/12.01g) = 4.788 moles of C
After calculating moles for each element, the values are approximately:
- C: 4.78 moles
- H: 5.39 moles
- N: 8.39 moles
- S: 9.58 moles
- O: Remainder
Divide all by the smallest moles number to get the ratio. The closest whole-number ratios for each element give us the empirical formula. The correct formula for penicillin with the given percentages, when rounded to whole numbers, is C16H18N2SO4 (Option A).