Glossary
Amphiprotic Substance
A substance that can act as both a Brønsted-Lowry acid (by donating a proton) and a Brønsted-Lowry base (by accepting a proton).
Example:
Water (H₂O) is an amphiprotic substance; it can donate a proton to become OH⁻ or accept a proton to become H₃O⁺.
Brønsted-Lowry Acid
A species that donates a proton (H⁺) in an acid-base reaction.
Example:
In the reaction H₂SO₄ + H₂O → HSO₄⁻ + H₃O⁺, sulfuric acid (H₂SO₄) acts as a Brønsted-Lowry Acid by donating a proton to water.
Brønsted-Lowry Base
A species that accepts a proton (H⁺) in an acid-base reaction.
Example:
When ammonia (NH₃) reacts with water to form NH₄⁺ and OH⁻, ammonia is the Brønsted-Lowry Base because it accepts a proton from water.
Conjugate Acid-Base Pair
Two species that are related to each other by the gain or loss of a single proton (H⁺). The acid has one more proton than its conjugate base.
Example:
In the equilibrium CH₃COOH + H₂O ⇌ CH₃COO⁻ + H₃O⁺, CH₃COOH and CH₃COO⁻ form a conjugate acid-base pair.
Equivalence Point
The point in a titration where the moles of acid are stoichiometrically equal to the moles of base, resulting in complete neutralization.
Example:
During the titration of HCl with NaOH, the equivalence point is reached when exactly enough NaOH has been added to react with all the HCl.
Hydronium Ion (H₃O⁺)
The ion formed when a proton (H⁺) associates with a water molecule (H₂O), often representing H⁺ in aqueous solutions.
Example:
When hydrochloric acid dissolves in water, it produces hydronium ions (H₃O⁺), which are responsible for the acidic properties of the solution.
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 moles of hydrogen and 2 moles of oxygen to make water, oxygen would be the limiting reactant because it runs out first.
Net Ionic Equation
An equation that shows only the species (ions, molecules, or solids) that are directly involved in a chemical reaction, omitting spectator ions.
Example:
For the reaction of a strong acid and strong base, the net ionic equation is always H⁺(aq) + OH⁻(aq) → H₂O(l).
Neutralization Reaction
A chemical reaction between an acid and a base that typically results in the formation of a salt and water.
Example:
Mixing stomach acid (HCl) with an antacid (like Mg(OH)₂) is a neutralization reaction that reduces acidity.
Proton (H⁺)
In the context of acid-base chemistry, a proton refers to a hydrogen ion (H⁺), which is essentially a hydrogen atom that has lost its electron.
Example:
During an acid-base reaction, the transfer of a proton (H⁺) from an acid to a base is the defining event.
Salt (in neutralization)
An ionic compound formed from the cation of a base and the anion of an acid during a neutralization reaction.
Example:
When hydrochloric acid reacts with sodium hydroxide, the resulting salt is sodium chloride (NaCl).
Spectator Ions
Ions that are present in a solution during a chemical reaction but do not participate in the reaction itself; they appear unchanged on both sides of the complete ionic equation.
Example:
In the reaction between NaCl and AgNO₃, the Na⁺ and NO₃⁻ ions are spectator ions because they remain dissolved in solution before and after the precipitation of AgCl.
Strong Acid
An acid that completely ionizes or dissociates in water, donating all its protons to water molecules.
Example:
Hydrochloric acid (HCl) is a strong acid because it fully dissociates into H⁺ and Cl⁻ ions in aqueous solution.
Strong Base
A base that completely dissociates in water, releasing all its hydroxide ions (OH⁻) or fully accepting protons.
Example:
Sodium hydroxide (NaOH) is a strong base commonly used in titrations because it fully dissociates into Na⁺ and OH⁻ ions.
Weak Acid
An acid that only partially ionizes or dissociates in water, meaning it does not donate all its protons.
Example:
Acetic acid (CH₃COOH), found in vinegar, is a weak acid because only a small fraction of its molecules ionize in water.
Weak Base
A base that only partially ionizes or accepts protons in water, meaning it does not fully produce hydroxide ions.
Example:
Ammonia (NH₃) is a weak base because it only partially reacts with water to form ammonium and hydroxide ions.