Chp. 3: Molecules, Moles, and Chemical Equations

Flashcards covering key vocabulary from Chapter 3: Molecules, Moles, and Chemical Equations, including concepts related to the mole, solutions, chemical equations, and types of aqueous reactions (precipitation, acid-base).

Mole

A laboratory-sized sample quantity of a substance that contains Avogadro's number of units (atoms, molecules, or ions), representing its molar mass in grams.

Avogadro's Number (NA)

The number of units (atoms, ions, or molecules) in one mole of a substance, which is approximately 6.02 x 10^23.

Molar Mass

The mass in grams of one mole of a substance (e.g., 18.0 g for 1 mol H₂O).

Chemical Equivalent

A quantity of a substance equal to one mole.

Molecular Mass

The sum of the atomic masses of all atoms indicated in the chemical formula of a molecular compound.

Formula Mass

The sum of the atomic masses of all atoms indicated in the chemical formula of an ionic compound.

Mass Percent

The amount of each element present in a compound, expressed as a percentage of the total mass of the compound.

Empirical Formula

A chemical formula that shows the simplest whole-number ratio of atoms in a compound.

Molecular Formula

A chemical formula that shows the actual number of atoms of each element in a molecule.

Solution

A homogenous mixture of two or more substances, which can be liquid, solid, or gaseous.

Solvent

The substance present in the greatest quantity in a solution, in which the solute is dissolved.

Solute

Substances other than the solvent in a solution, which are dissolved in the solvent.

Aqueous Solution (aq)

A liquid solution in which the solvent is water.

Concentration

The amount of solute present in a given quantity of solvent or solution.

Molarity (M)

A measure of concentration, defined as the moles of solute per liter of solution (molar concentration).

Dilution

The procedure for preparing a less concentrated solution from a more concentrated (stock) solution.

Stock Solution

A concentrated solution stored for later dilution to a desired volume and concentration.

Chemical Equation

A representation of a chemical reaction using chemical formulas to show the reactants and products, along with stoichiometric coefficients and phases.

Combustion Reaction

A chemical reaction, typically rapid, between a substance and an oxidant (usually oxygen) to produce heat and light. For hydrocarbons, products are carbon dioxide and water.

Hydrocarbon

A compound composed solely of hydrogen and carbon atoms.

Reactants

The starting substances (elements, compounds, or ions) that undergo change in a chemical reaction.

Products

The substances (elements, compounds, or ions) that are formed as a result of a chemical reaction.

Stoichiometric Coefficients

Numbers in a balanced chemical equation that indicate the fixed molar ratios of reactants and products.

Balanced Chemical Equation

A chemical equation in which the number of atoms of each element is the same on both the reactant and product sides, satisfying the law of conservation of mass.

Solubility

The maximum amount of a solute that can dissolve in a given amount of solvent at a specific temperature.

Precipitate

An insoluble solid compound that forms and separates from a solution during a chemical reaction.

Electrolyte

A substance that, when dissolved in water, produces ions and conducts electricity.

Non-Electrolyte

A substance that does not produce ions when dissolved in water and therefore does not conduct electricity.

Weak Electrolyte

A solute that dissociates only partially into ions in solution and conducts electricity poorly (e.g., weak acids and weak bases).

Strong Electrolyte

A substance that completely or nearly completely dissociates into ions in solution and conducts electricity well (e.g., soluble salts, strong acids, and strong bases).

Soluble Molecular Compounds

Compounds that dissolve in solution while remaining intact as molecules, surrounded by polar water molecules.

Soluble Ionic Solids (Salts)

Ionic compounds that dissociate to form ions when dissolved in an aqueous solution.

Precipitation Reaction

A type of aqueous reaction that results in the formation of an insoluble solid (precipitate) from the mixing of two solutions.

Molecular Equation

A chemical equation that shows all reactants and products as intact molecules or compounds, without indicating their ionic character in solution.

Spectator Ions

Ions present in a solution that do not participate directly in a chemical reaction and remain unchanged throughout the reaction.

Total Ionic Equation

A chemical equation that shows all soluble ionic compounds as dissociated ions in solution, while insoluble solids, gases, and undissociated molecular compounds are written in their molecular forms.

Net Ionic Equation

A chemical equation that includes only the species directly involved in a chemical reaction, omitting any spectator ions.

Acid-Base Reaction

A chemical reaction that occurs between an acid and a base, often resulting in the formation of water and a salt (neutralization).

Acid

A substance that produces hydrogen ions (H+) when dissolved in water.

Base

A substance that produces hydroxide ions (OH-) when dissolved in water.

Strong Acid

An acid that dissociates completely into ions in an aqueous solution and is therefore a strong electrolyte (e.g., HCl, HBr, HI, HNO₃, H₂SO₄, HClO₄).

Strong Base

A base that dissociates completely into ions in an aqueous solution and is therefore a strong electrolyte (e.g., NaOH, LiOH, KOH, Ba(OH)₂).

Weak Acid

An acid that dissociates only partially into ions in an aqueous solution and is therefore a weak electrolyte (e.g., HF, HC₂H₃O₂).

Weak Base

A base that produces very little hydroxide ions (OH-) in solution and is therefore a weak electrolyte (e.g., NH₃).

Neutralization Reaction

A type of acid-base reaction in which an acid and a base react to form water and a salt.