Final answer:
By converting the mass percentages to moles and then finding the simplest whole number ratio, the empirical formula is determined to be C2H5, which matches the molecular formula in option C) C2H5.
Step-by-step explanation:
The question is asking to identify the molecular formula of a hydrocarbon based on the given percentages of carbon and hydrogen by mass. To solve this, we first need to determine the empirical formula using the mass percentages.
Assume we have 100 grams of the compound, then we would have 82.7 grams of carbon and 17.3 grams of hydrogen. Since we know the atomic masses (carbon = 12 g/mol, hydrogen = 1 g/mol), we can find the number of moles of each element: carbon moles = 82.7 g / 12 g/mol = 6.892 moles, hydrogen moles = 17.3 g / 1 g/mol = 17.3 moles.
To find the simplest whole number ratio, divide each by the smallest number of moles: carbon ratio = 6.892/6.892 = 1, hydrogen ratio = 17.3/6.892 ≈ 2.51. Since we can't have a fraction of a hydrogen atom, we multiply both ratios by a factor (approximately 2 in this case) to get whole numbers: carbon = 1 x 2 = 2, hydrogen = 2.51 x 2 = 5. Therefore, the empirical formula is C2H5. Looking at the options provided, the molecular formula that matches this empirical formula is option C) C2H5.