The foul odor of rancid butter is due largely to butyric acid, a compound containing carbon, hydrogen, and oxygen. Combustion analysis of a 4.30-g sample of butyric acid produces 8.59 g CO₂ and 3.52 g H₂O. Determine the empirical formula of butyric acid.

Verified step by step guidance

1. Calculate the moles of carbon in the CO2 produced. Use the molar mass of CO2 (44.01 g/mol) and the fact that each mole of CO2 contains one mole of carbon.
2. Calculate the moles of hydrogen in the H2O produced. Use the molar mass of H2O (18.02 g/mol) and the fact that each mole of H2O contains two moles of hydrogen.
3. Determine the mass of carbon and hydrogen in the original sample using the moles calculated and the atomic masses of carbon (12.01 g/mol) and hydrogen (1.008 g/mol).
4. Calculate the mass of oxygen in the original sample by subtracting the mass of carbon and hydrogen from the total mass of the sample (4.30 g).
5. Convert the mass of oxygen to moles using the atomic mass of oxygen (16.00 g/mol), then determine the simplest whole number ratio of moles of C, H, and O to find the empirical formula.

Key Concepts

Empirical Formula

The empirical formula of a compound represents the simplest whole-number ratio of the elements present in that compound. It is derived from the relative amounts of each element, typically determined through experimental data such as combustion analysis. For butyric acid, the empirical formula can be calculated by converting the mass of carbon and hydrogen obtained from combustion into moles and then finding the simplest ratio.

Combustion Analysis

Combustion analysis is a technique used to determine the composition of organic compounds by burning a known mass of the sample in excess oxygen. The products of combustion, primarily carbon dioxide (CO2) and water (H2O), are measured to calculate the amounts of carbon and hydrogen in the original sample. This method is essential for finding the empirical formula of compounds like butyric acid.

Stoichiometry

Stoichiometry is the branch of chemistry that deals with the quantitative relationships between the reactants and products in a chemical reaction. It allows chemists to calculate the amounts of substances consumed and produced in a reaction based on balanced chemical equations. In the context of butyric acid, stoichiometry is used to relate the masses of CO2 and H2O produced to the moles of carbon and hydrogen in the original compound.