Formulae, Equations and Amounts of Substance

Vocabulary practice flashcards covering fundamental stoichiometry concepts, formulas, concentrations, ideal gas laws, reaction yields, and acid-base chemistry definitions from the lecture notes.

Mole

The amount of substance in grams that has the same number of particles as there are atoms in $12\text{ grams}$ of carbon-12.

Relative atomic mass

The weighted mean mass of one atom compared to one twelfth of the mass of one atom of carbon-12.

Molar mass

The mass in grams of $1\text{ mole}$ of a substance, given the unit of $g\,mol^{-1}$.

Hydrated salt

A salt containing water of crystallisation.

Water of crystallisation

The water chemically bound in hydrated salt crystals that can be removed as water vapour upon heating.

Avogadro's constant

The constant stating that one mole of any specified entity (atoms, molecules, or ions) contains $6.02 \times 10^{23}$ of that entity.

Density

The mass of a substance divided by its volume ($\text{density} = \frac{\text{mass}}{\text{volume}}$), usually given in $g\,cm^{-3}$.

Parts per million (ppm)

A measurement of concentration by mass defined as $\frac{\text{mass of substance in mixture}}{\text{total mass of mixture}} \times 1\,000\,000$.

Empirical formula

The simplest ratio of atoms of each element in a compound.

Molecular formula

The actual number of atoms of each element in a compound.

Solution

A mixture formed when a solute dissolves in a solvent.

Molar concentration

The amount in moles of the solute divided by the volume of the solution in $dm^3$, with units of $mol\,dm^{-3}$ or $M$.

Mass concentration

The concentration of a solution measured as mass of solute per volume of solution ($\frac{\text{mass}}{\text{volume}}$), with the unit $g\,dm^{-3}$.

Ideal gas equation

The equation $PV = nRT$, where $P$ is pressure in $Pa$, $V$ is volume in $m^3$, $n$ is moles, $R = 8.31\,J\,K^{-1}\,mol^{-1}$, and $T$ is temperature in $K$.

Percentage yield

A measure of practical efficiency calculated as $\frac{\text{actual yield}}{\text{theoretical yield}} \times 100$.

Percentage atom economy

A measure of process efficiency calculated as $\frac{\text{mass of useful products}}{\text{mass of all reactants}} \times 100$.

Displacement reaction

A reaction in which a more reactive metal displaces a less reactive metal from its compound, or a halogen that is a stronger oxidising agent displaces a halogen with lower oxidising power.

Precipitation reaction

A reaction in which insoluble salts are prepared by mixing appropriate solutions of ions so that a solid precipitate is formed.

Precipitate

An insoluble solid that forms out of solution during a precipitation reaction.

Spectator ions

Ions that do not participate in a chemical reaction, identified by not changing state and not changing oxidation number.

Salt

A compound formed when the $H^+$ ion of an acid is replaced by a metal ion or an ammonium ion.

Base

A substance that neutralises acids, with common examples being metal oxides, metal hydroxides, and ammonia.

Alkali

A soluble base that releases $OH^-$ ions in aqueous solution.