Glossary
Aqueous Solution
A solution in which water acts as the solvent, dissolving a solute to form a homogeneous mixture.
Example:
When you dissolve table salt in water to make a saline solution, you've created an aqueous solution.
Complete Ionic Equation
A chemical equation that represents all soluble ionic compounds as dissociated ions in solution, while insoluble compounds remain as intact formulas.
Example:
Before writing a net ionic equation, you first write the complete ionic equation to show all dissolved ions, like 2K⁺(aq) + 2I⁻(aq) + Pb²⁺(aq) + 2NO₃⁻(aq) for the lead iodide reaction.
Insoluble
Describes a substance that does not dissolve significantly in a given solvent, often forming a solid precipitate in aqueous solutions.
Example:
If you try to dissolve sand in water, you'll find it's largely insoluble, remaining as a solid at the bottom.
Ion-Dipole Interaction
An attractive force that occurs between an ion and a polar molecule, where the oppositely charged end of the polar molecule is attracted to the ion.
Example:
When NaCl dissolves in water, the positive Na⁺ ions are surrounded by the negative oxygen ends of water molecules, demonstrating ion-dipole interactions.
Limiting Reactant
The reactant in a chemical reaction that is completely consumed first, thereby determining the maximum amount of product that can be formed.
Example:
If you have 5 hot dogs but only 3 buns, the buns are the limiting reactant because they determine you can only make 3 hot dog meals.
Net Ionic Equation
A chemical equation that shows only the ions and molecules directly involved in a chemical reaction, excluding spectator ions.
Example:
For the reaction of silver nitrate and sodium chloride, the net ionic equation simplifies to Ag⁺(aq) + Cl⁻(aq) → AgCl(s), showing only the species that form the precipitate.
Polar Molecule
A molecule that has a net dipole moment due to the unequal sharing of electrons, resulting in partial positive and negative charges on different parts of the molecule.
Example:
Water (H₂O) is a classic polar molecule because oxygen pulls electrons more strongly than hydrogen, creating distinct positive and negative regions.
Precipitate
An insoluble solid that forms from a solution during a chemical reaction, separating out from the liquid phase.
Example:
Mixing solutions of silver nitrate and sodium chloride causes a white solid, silver chloride, to form as a precipitate.
Solubility Rules
A set of guidelines used to predict whether an ionic compound will dissolve in water or form a precipitate.
Example:
Using solubility rules, you can quickly determine that all compounds containing nitrate ions are soluble.
Spectator Ions
Ions that are present in a solution during a chemical reaction but do not participate in the reaction itself, remaining unchanged on both sides of the equation.
Example:
In the reaction forming silver chloride, sodium ions and nitrate ions are spectator ions because they stay dissolved and don't form the precipitate.