Chapter 1-6 Review: Empirical Formulas, Combustion Analysis, and Molarity

Vocabulary flashcards covering key concepts from the lecture notes on empirical formulas, combustion analysis, and molarity.

Empirical formula

The simplest whole-number ratio of elements in a compound, obtained by converting percent composition to moles and reducing by the smallest mole value.

Percent composition (mass percent)

The fraction of a compound's mass contributed by each element, expressed as a percentage of the total mass.

100-gram sample

A convenient assumed total mass used to convert mass percentages to grams in empirical formula calculations.

Gram to mole conversion

Using atomic or molar masses to convert a mass in grams to moles.

Molar ratio

The ratio of moles of elements in a compound, used to determine the empirical formula.

Molecular formula

The actual numbers of each element in a molecule; equals an integer multiple of the empirical formula, determined by the compound’s molar mass.

Empirical mass

The molar mass of the empirical formula (sum of atomic masses in the empirical formula).

Smallest mole value

The smallest number of moles among elements used to obtain the empirical formula by dividing each by this value.

CO2 to carbon

In combustion analysis, the amount of carbon in the original sample is derived from the moles of CO2 produced.

H2O to hydrogen

In combustion analysis, the amount of hydrogen in the original sample is derived from the moles of H2O produced.

Excess oxygen

Oxygen used as a reactant in combustion that does not originate from the sample; not counted in the sample’s composition.

Oxygen mass by subtraction

The mass of oxygen in the original sample found by subtracting the masses of carbon and hydrogen (in grams) from the original sample mass.

Combustion analysis

A method to determine a compound’s elemental composition by burning a sample in excess oxygen and analyzing CO2 and H2O.

Molarity

The concentration of a solution expressed as moles of solute per liter of solution (mol/L).

Molality

The concentration of a solution expressed as moles of solute per kilogram of solvent (mol/kg).

Aqueous

Describes a solution in which the solvent is water.

Solution

A homogeneous mixture of solute dissolved in solvent.

Solute

The substance dissolved in the solvent.

Solvent

The substance doing the dissolving, typically present in the greatest amount.

100 g rule

Using a 100-gram sample to simplify percent-to-gram conversion when calculating empirical formulas.

Fractional subscripts and rounding

Converting fractional subscripts to whole numbers by multiplying by appropriate factors (e.g., 3 for 1/3, 4 for 1/4, 2 for 1/2, 5 for 1/5).