Moles and Stoichiometry Lecture

30 vocabulary flashcards covering key terms from the lecture on moles, formula masses, percentage composition, empirical and molecular formulas, and stoichiometric calculations.

Mole

The amount of substance containing as many specified particles as there are atoms in exactly 12 g of carbon-12; symbol mol.

Avogadro's Number

6.02 × 10^23, the number of particles in one mole of any substance.

Relative Atomic Mass (Ar)

The weighted average mass of an atom of an element compared with 1⁄12 of the mass of a carbon-12 atom.

Relative Molecular Mass (Mr)

The mass of a molecule compared to 1⁄12 of the mass of a carbon-12 atom, calculated by summing the relative atomic masses of all atoms in the molecule.

Relative Formula Mass (Mr)

The sum of the relative atomic masses of the atoms in a formula unit of an ionic compound.

Formula Unit

The simplest ratio of ions represented in the formula of an ionic compound.

Percentage Composition by Mass

The mass percentage of each element in a compound, found with (mass of element in 1 mol compound ÷ molar mass of compound) × 100 %.

Hydrated Salt

An ionic compound that contains a fixed ratio of water molecules within its crystal lattice, e.g., CuSO₄·5H₂O.

Anhydrous Salt

A salt from which all water of crystallisation has been removed.

Empirical Formula

The simplest whole-number ratio of atoms of each element in a compound.

Molecular Formula

A formula showing the actual number of each type of atom present in one molecule of a substance.

Displayed Formula

A structural representation that shows every atom and every bond in a molecule.

Structural Formula

A formula that indicates the arrangement of atoms in a molecule without necessarily showing every bond.

Molar Mass

The mass of one mole of a substance, numerically equal to its Mr in grams per mole.

Concentration (mol/dm³)

The amount of solute in moles dissolved per cubic decimetre of solution.

Concentration (g/dm³)

The amount of solute in grams dissolved per cubic decimetre of solution.

Molar Volume (of a gas)

The volume occupied by one mole of any gas at room temperature and pressure (r.t.p.), approximately 24 dm³.

Diatomic Element

An element that exists naturally as molecules containing two atoms, e.g., H₂, N₂, O₂, F₂, Cl₂, Br₂, I₂.

Balanced Chemical Equation

A chemical equation in which the number of each type of atom is the same on both sides, reflecting conservation of mass.

Stoichiometry

The quantitative relationships between reactants and products in a balanced chemical equation.

Stoichiometric Ratio

The fixed molar proportion of reactants and products indicated by coefficients in a balanced equation.

Standard Solution

A solution of accurately known concentration used for titrations.

Limiting Reactant

The reactant that is completely consumed first, thus limiting the amount of product formed in a reaction.

Mass–Mole Relationship

The equation n = m ⁄ M linking number of moles (n) to mass (m) and molar mass (M).

Volume–Mole Relationship

For gases at r.t.p., moles can be calculated from volume using n = V ⁄ 24 dm³.

Concentration–Mole Relationship

The equation n = c × V, connecting moles to concentration and volume of a solution.

Avogadro's Constant

Another term for Avogadro’s number, 6.02 × 10^23 particles per mole.

Water of Crystallisation

The fixed number of water molecules chemically bound within a hydrated salt’s crystal structure.

Avogadro’s Law

The gas law stating that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.

Molarity

Another term for concentration expressed in moles per cubic decimetre (mol/dm³).