SL IB Chemistry: Counting Particles by Mass - The Mole

Vocabulary flashcards covering core stoichiometric concepts, mole theory, empirical/molecular formulas, solutions, and gas laws from the IB Chemistry syllabus.

Avogadro constant ($N_A$ or $L$)

The number of particles equivalent to the relative atomic mass or molecular mass of a substance in grams, with a value equal to $6.02 \times 10^{23}\,mol^{-1}$.

Mole

The amount of a substance that contains the same number of fundamental units as there are atoms in exactly $12.00\,g$ of $^{12}C$.

Molar mass ($M$)

The mass of a substance containing one mole ($6.02 \times 10^{23}$) of particles, with the units of $g\,mol^{-1}$.

Relative atomic mass ($A_r$)

The weighted average mass of one atom of an element compared to one twelfth the mass of a carbon-12 atom, which has no units because it is a ratio.

Relative formula mass ($M_r$)

The sum of the relative atomic masses of the atoms in a formula unit, used specifically for compounds containing ions and calculated identically to relative molecular mass.

Molecular formula

The formula that shows the actual number and type of each atom present in a molecule.

Empirical formula

The simplest whole number ratio of the atoms of each element present in one molecule or formula unit of a compound.

Concentration

The amount of solute dissolved in a solvent to make $1\,dm^3$ of solution.

Solute

The substance that dissolves in a solvent to form a solution.

Solvent

The liquid substance (often water) in which a solute dissolves to form a solution.

Concentrated solution

A solution that has a high concentration of solute.

Dilute solution

A solution that has a low concentration of solute.

Parts per million (ppm)

A unit used for extremely low concentrations, defined as a mass of $1\,mg$ of solute dissolved in $1\,dm^3$ (or $1\,kg$) of water, equivalent to a concentration of $1$ in a million ($10^6$).

Avogadro's law

The principle stating that equal volumes of gases at the same temperature and pressure contain the same number of molecules.

Standard temperature and pressure (STP)

A reference set of standard conditions defined as a temperature of $0^\circ\text{C}$ ($273\,\text{K}$) and a pressure of $100\,\text{kPa}$, under which one mole of any gas has a molar volume of $22.7\,dm^3\,mol^{-1}$.

Limiting reactant

The reacting substance that is completely consumed first in a chemical reaction, thereby determining and limiting the total amount of product formed.