Determine the empirical formula of an organic compound...

Determine the empirical formula of an organic compound containing only $\mathrm{C}$ and $\mathrm{H}$ given that combustion of a $1.50-\mathrm{g}$ sample of the compound produces $4.71 \mathrm{g} \mathrm{CO}_{2}$ and $1.93 \mathrm{g} \mathrm{H}_{2} \mathrm{O}$.

Key Concepts

Mole Calculations and Stoichiometry

Mole calculations are fundamental in converting measured masses into moles, a central step in stoichiometry, which deals with the quantitative relationships between reactants and products in chemical reactions. In the context of combustion analysis, converting the mass of carbon dioxide and water to moles allows for the determination of the number of moles of carbon and hydrogen present in the original compound. Stoichiometry then uses these values to establish the molar ratios, which are key to deriving the empirical formula of the substance.

Combustion Analysis

Combustion analysis is an analytical technique used to determine the elemental composition of an organic compound by burning it in oxygen and analyzing the amount of combustion products formed. By measuring the masses of products such as carbon dioxide and water, one can deduce the quantity of carbon and hydrogen in the original sample. This method is particularly valuable for compounds containing only carbon and hydrogen, as the conversion from products back to the elements is straightforward.

Empirical Formula Determination

Empirical formula determination involves finding the simplest whole number ratio of elements present in a compound. Once the mass of each element (as determined from combustion analysis) is converted to moles, these mole quantities are compared to find the smallest possible ratio. This process yields the empirical formula, which represents the basic composition of the compound without providing information on the actual number of atoms per molecule as found in the molecular formula.

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