(a) Combustion analysis of 50.0 mg of benzene, a commonly used solvent composed of carbon and hydrogen, gives 34.6 mg of H₂O and 169.2 mg of CO₂. What is the empirical formula of benzene?

Verified step by step guidance

1. Convert the mass of CO_2 to moles using its molar mass (44.01 g/mol).
2. Determine the moles of carbon in CO_2 by recognizing that each mole of CO_2 contains one mole of carbon.
3. Convert the mass of H_2O to moles using its molar mass (18.02 g/mol).
4. Determine the moles of hydrogen in H_2O by recognizing that each mole of H_2O contains two moles of hydrogen.
5. Calculate the simplest whole number ratio of moles of carbon to moles of hydrogen to find the empirical formula.

Key Concepts

Combustion Analysis

Combustion analysis is a technique used to determine the composition of organic compounds by burning them in excess oxygen. The products of combustion, typically 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 deriving empirical formulas from the mass of the products formed.

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 mass of each element obtained from combustion analysis and is crucial for understanding the basic composition of the substance. For example, if a compound contains carbon and hydrogen in a 1:1 ratio, its empirical formula would be CH.

Stoichiometry

Stoichiometry involves the calculation of reactants and products in chemical reactions based on the conservation of mass. In combustion analysis, stoichiometric relationships allow us to convert the masses of CO2 and H2O produced into moles of carbon and hydrogen, respectively. This is fundamental for determining the empirical formula, as it ensures accurate ratios of the elements are used.