Chemistry Chapter 3 - Composition of Substances and Solutions Flashcards

Vocabulary flashcards based on OpenStax Chemistry 2e Chapter 3 covering formula mass, the mole concept, empirical/molecular formulas, molarity, and solution dilutions.

Formula Mass

The sum of the average atomic masses of all the atoms in a substance's formula.

Molecular Mass

The formula mass of a covalent substance, which exists as discrete molecules.

Mole

The amount of a substance that contains as many elementary entities (such as atoms, molecules, or ions) as there are atoms in a sample of pure carbon-12 weighing exactly $12.00\,\text{g}$.

Avogadro's Number ($N_A$)

The constant representing the number of entities composing one mole, determined to be $6.02214179 \times 10^{23}$ (commonly rounded to $6.022 \times 10^{23}$).

Amedeo Avogadro

Italian scientist (1776–1856) who in 1811 first proposed that the volume of a gas (at a given pressure and temperature) is proportional to the number of atoms or molecules regardless of the nature of the gas.

Jean Perrin

Physicist who coined the name Avogadro's number in 1909, defining it as the number of molecules in exactly 32 grams of oxygen gas.

Molar Mass

The mass in grams of 1 mole of an element or compound, expressed in units of grams per mole ($\text{g}\,\text{mol}^{-1}$), which is numerically equivalent to its atomic or formula mass in $\text{amu}$.

Percent Composition

The percentage by mass of each element present in a compound.

Empirical Formula

A chemical formula showing the smallest whole-number ratio of subscripts of elements present in a compound.

Molecular Formula

A formula obtained by multiplying each subscript in the empirical formula by $n$, where $n = \frac{\text{molecular or molar mass}}{\text{empirical formula mass}}$.

Solution

Another term for a homogeneous mixture, characterized by uniform composition and properties throughout its entire volume.

Concentration

The relative amount of a given solution component.

Solvent

The component of a solution with a concentration that is significantly greater than that of all other components.

Solute

The component of a solution that is typically present at a much lower concentration than the solvent.

Aqueous Solution

A solution in which water is the solvent.

Molarity ($M$)

A concentration unit defined as the number of moles of solute in exactly 1 liter ($1\,\text{L}$) of the solution: $M = \frac{\text{mol solute}}{\text{L solution}}$.

Dilution

The process whereby the concentration of a solution is lessened by the addition of solvent.

Dilution Equation

The mathematical relationship $M_1 V_1 = M_2 V_2$, derived from the fact that the molar amount of solute ($n$) does not change during dilution.

Hematite

An iron oxide mineral that is used in jewelry.

Dopamine ($\text{C}_8\text{H}_{11}\text{NO}_2$)

A neurotransmitter molecule involved in a number of neurological processes that transmits chemical signals between neurons across synapses.