(a) Polychlorinated biphenyls (PCBs) were compounds used as coolants in transformers and capacitors, but their production was banned by the U.S. Congress in 1979 because they are highly toxic and persist in the environment. When 1.0 g of a PCB containing carbon, hydrogen, and chlorine was subjected to combustion analysis, 1.617 g of CO₂. and 0.138 g of H₂O were produced. What is the empirical formula?

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 finding the empirical formula of a compound, as it provides the necessary data on the elemental composition.

The empirical formula of a compound represents the simplest whole-number ratio of the elements present in that compound. It is derived from the amounts of each element obtained from combustion analysis. For example, if a compound contains carbon, hydrogen, and chlorine, the empirical formula will reflect the ratio of these elements based on their respective moles calculated from the combustion products.

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 combustion analysis, stoichiometry is used to convert the masses of CO2 and H2O produced into moles of carbon and hydrogen, which are then used to determine the empirical formula.