Chapter 3: Stoichiometry of Formulas and Equations

Definition-style flashcards covering the fundamental concepts of stoichiometry, includes mass relationships, empirical/molecular formulas, and solution chemistry based on the lecture slides.

Mole (mol)

The amount of a substance that contains the same number of entities as there are atoms in exactly $12\,g$ of carbon-12.

Avogadro’s number (N)

$6.022 \times 10^{23}$, representing the number of entities in one mole of a substance.

Isotopic mass

The mass of an isotope of an element, measured in $amu$.

Atomic mass

The average of the masses of the naturally occurring isotopes of an element weighted according to their abundance, measured in $amu$.

Molecular (or formula) mass

The sum of the atomic masses of the atoms (or ions) in a molecule (or formula unit), also called molecular weight; measured in $amu$.

Molar mass (M)

The mass of 1 mole of chemical entities (atoms, ions, molecules, formula units), measured in $g/mol$. It is also called gram-molecular weight.

Mass % of element X

$\frac{\text{moles of X in formula} \times \text{molar mass of X (amu)}}{\text{molecular (or formula) mass of compound (amu)}} \times 100$.

Empirical Formula

The simplest formula for a compound that agrees with the elemental analysis and gives rise to the smallest set of whole numbers of atoms.

Molecular Formula

The formula of the compound as it exists, which may be a multiple of the empirical formula.

Constitutional Isomers

Different compounds with the same molecular formula, such as Ethanol and Dimethyl Ether.

Balancing Coefficients

Numbers used in a chemical equation that refer to both individual chemical entities and moles of chemical entities.

Limiting Reactant

The reactant that is completely consumed in a reaction and determines the maximum amount of product that can be formed.

Percent Yield

$\frac{\text{actual yield}}{\text{theoretical yield}} \times 100$.

Molarity (M)

The number of moles of solute per liter of solution.

Isotonic saline

A $0.15\,M$ aqueous solution of $NaCl$ that simulates the total concentration of ions found in many cellular fluids.