Estrone, which contains only carbon, hydrogen, and oxygen, is a female sexual hormone in the urine of pregnant women. Combustion analysis of a 1.893-g sample of estrone produces 5.545 g of CO₂ and 1.388 g H₂O. The molar mass of estrone is 270.36 g/mol. Find its molecular formula.

Verified step by step guidance

1. Determine the moles of carbon in the CO2 produced. Use the molar mass of CO2 (44.01 g/mol) to find the moles of CO2, then use the ratio of carbon in CO2 to find the moles of carbon.
2. Determine the moles of hydrogen in the H2O produced. Use the molar mass of H2O (18.02 g/mol) to find the moles of H2O, then use the ratio of hydrogen in H2O to find the moles of hydrogen.
3. Calculate the mass of carbon and hydrogen in the original sample using their respective moles and atomic masses (C: 12.01 g/mol, H: 1.008 g/mol).
4. Subtract the mass of carbon and hydrogen from the total mass of the sample to find the mass of oxygen. Then, calculate the moles of oxygen using its atomic mass (O: 16.00 g/mol).
5. Determine the empirical formula by finding the simplest whole number ratio of moles of C, H, and O. Then, use the molar mass of estrone to find the molecular formula by comparing the empirical formula mass to the given molar mass.

Key Concepts

Combustion Analysis

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 (CO2) and water (H2O). By measuring the masses of these products, one can calculate the amounts of carbon and hydrogen in the original sample, which are essential for determining the empirical formula of the compound.

Empirical Formula

The empirical formula represents the simplest whole-number ratio of the elements in a compound. It is derived from the amounts of each element obtained from combustion analysis. To find the empirical formula, the moles of each element are calculated and then simplified to the smallest ratio, which serves as a foundational step in determining the molecular formula.

Molecular Formula

The molecular formula indicates the actual number of atoms of each element in a molecule of a compound. It is derived from the empirical formula by multiplying it by a whole number, which is determined by comparing the molar mass of the compound to the molar mass of the empirical formula. This formula provides more detailed information about the compound's structure and composition.