Formula Weight, Molar Mass, and Stoichiometry Review

Vocabulary flashcards covering formula weight, molar mass, reaction classifications, stoichiometry conversions, and empirical and molecular formula calculations.

Formula Weight (FW)

The sum of the atomic weights of each atom in a chemical formula, expressed in atomic mass units ($\text{amu}$), utilized for both ionic and covalent compounds.

Molar Mass (MM)

The mass of one mole of a substance expressed in grams per mole ($\text{g/mol}$), which is numerically equivalent to its formula weight in $\text{amu}$.

Grams-to-Moles Conversion Formula

The formula used to calculate the number of moles from a given mass: $\text{Moles} = \frac{\text{mass}(\text{g})}{\text{MolarMass}(\text{g/mol})}$.

Moles-to-Grams Conversion Formula

The formula used to calculate the mass of a substance from moles: $\text{Mass}(\text{g}) = \text{Moles} \times \text{MolarMass}(\text{g/mol})$.

Single Displacement Reaction

A chemical reaction in which one element displaces another in a compound, exemplified by $1\text{SnO}_2 + 2\text{H}_2 \rightarrow 1\text{Sn} + 2\text{H}_2\text{O}$, $4\text{NH}_3 + 5\text{O}_2 \rightarrow 4\text{NO} + 6\text{H}_2\text{O}$, and $2\text{Fe} + 6\text{HC}_2\text{H}_3\text{O}_2 \rightarrow 2\text{Fe}(\text{C}_2\text{H}_3\text{O}_2)_3 + 3\text{H}_2$.

Double Displacement Reaction

A chemical reaction characterized by the exchange of bonds or ions between two reacting species, exemplified by $3\text{KOH} + 1\text{H}_3\text{PO}_4 \rightarrow 1\text{K}_3\text{PO}_4 + 3\text{H}_2\text{O}$, $1\text{B}_2\text{Br}_6 + 6\text{HNO}_3 \rightarrow 2\text{B}(\text{NO}_3)_3 + 6\text{HBr}$, and $1\text{Na}_3\text{PO}_4 + 3\text{HCl} \rightarrow 3\text{NaCl} + 1\text{H}_3\text{PO}_4$.

Combustion Reaction

A chemical reaction involving an organic substance reacting with oxygen to produce carbon dioxide and water, exemplified by $1\text{C}_3\text{H}_8 + 5\text{O}_2 \rightarrow 3\text{CO}_2 + 4\text{H}_2\text{O}$ and $1\text{C}_2\text{H}_6\text{O} + 3\text{O}_2 \rightarrow 2\text{CO}_2 + 3\text{H}_2\text{O}$.

Combination (Synthesis) Reaction

A chemical reaction in which two or more simple substances combine to form a single product, exemplified by $3\text{Mg} + 1\text{N}_2 \rightarrow 1\text{Mg}_3\text{N}_2$.

Decomposition Reaction

A chemical reaction in which a single compound breaks down into two or more elements or simpler compounds, exemplified by $2\text{NaN}_3 \rightarrow 2\text{Na} + 3\text{N}_2$.

Avogadro's Number

The standard conversion constant representing the number of constituent particles (such as atoms, molecules, or formula units) per mole, equal to $6.022 \times 10^{23}\text{ units/mol}$.

Percent Composition

The percentage by mass of each individual element present in a compound, calculated by dividing the total element mass in one mole of compound by the compound molar mass and multiplying by $100$.

Empirical Formula

The chemical formula that gives the simplest whole-number molar ratio of atoms of each element in a compound, such as $\text{C}_7\text{H}_7\text{NO}_2$, $\text{CH}_2\text{O}$, $\text{CH}_2$, or $\text{Na}_2\text{CO}_3$.

Empirical Formula Weight

The sum of the atomic weights of all the atoms present in the empirical formula of a compound, such as $30.03\text{ g/mol}$ for $\text{CH}_2\text{O}$ or $14.03\text{ g/mol}$ for $\text{CH}_2$.

Molecular Formula

The actual chemical formula of a molecular compound, determined by multiplying the empirical formula by an integer multiple $n$, where $n = \frac{\text{Molar Mass}}{\text{Empirical Weight}}$ (e.g., $(\text{CH}_2\text{O})_6 = \text{C}_6\text{H}_{12}\text{O}_6$ or $(\text{CH}_2)_4 = \text{C}_4\text{H}_8$).