The stimulant amphetamine contains only carbon, hydrogen, and nitrogen. Combustion analysis of a 42.92 mg sample of amphetamine gives 37.187 mg of H2O and 125.75 mg of CO2. If the molar mass of amphetamine is less than 160 g/mol, what is its molecular formula?

Combustion analysis is a technique used to determine the elemental composition of organic compounds. In this process, a sample is burned in excess oxygen, producing carbon dioxide and water. The masses of these products are measured, allowing for the calculation of the amounts of carbon, hydrogen, and other elements in the original sample.

The empirical formula represents the simplest whole-number ratio of the elements in a compound. To derive it, the moles of each element are calculated from the mass of the products obtained in combustion analysis. This formula provides essential information about the composition of the compound, which is a stepping stone to determining the molecular formula.

The molecular formula indicates the actual number of atoms of each element in a molecule of a compound. It can be derived from the empirical formula by multiplying it by a whole number, which is determined by the molar mass of the compound. In this case, knowing that the molar mass of amphetamine is less than 160 g/mol helps in identifying the correct molecular formula based on the empirical formula.