| Term | Definition |
|---|---|
| buffer capacity | The amount of acid or base that a buffer solution can neutralize while maintaining a relatively constant pH. |
| buffer components | The conjugate acid-base pair that makes up a buffer solution and determines its pH and capacity. |
| concentration ratio | The ratio of the concentration of the conjugate base to the concentration of the conjugate acid, [A-]/[HA], in a buffer solution. |
| conjugate acid | The species formed when a base accepts a proton; the acid form in an acid-base conjugate pair. |
| conjugate base | The species formed when an acid donates a proton; the base form in an acid-base conjugate pair. |
| Term | Definition |
|---|---|
| autoionization | The process by which water molecules react with each other to produce hydronium and hydroxide ions in equilibrium. |
| hydronium ion | The aqueous ion H3O+(aq) formed when a hydrogen ion bonds with a water molecule; represents the form of hydrogen ion in aqueous solution. |
| hydroxide ion | The negatively charged ion OH− produced when water autoionizes or when a base dissolves in water. |
| Kw | The ion product constant for water, equal to [H3O+][OH−] = 1.0 × 10−14 at 25°C, representing the equilibrium constant for water autoionization. |
| neutral solution | An aqueous solution in which pH = pOH = 7.0 at 25°C, meaning the concentrations of hydronium and hydroxide ions are equal. |
| pH | A logarithmic scale used to express the concentration of hydronium ions in a solution, calculated as −log[H3O+]. |
| pKw | The negative logarithm of Kw; equals 14.0 at 25°C and represents the sum of pH and pOH in any aqueous solution at that temperature. |
| pOH | A logarithmic scale used to express the concentration of hydroxide ions in a solution, calculated as −log[OH−]. |
| Term | Definition |
|---|---|
| hydroxide ion | The negatively charged ion OH− produced when water autoionizes or when a base dissolves in water. |
| Le Châtelier's principle | A principle stating that when a system at equilibrium is disturbed, the system shifts to counteract the disturbance and re-establish equilibrium. |
| pH-sensitive solubility | The property of a salt's solubility changing in response to changes in pH of the solution. |
| salt solubility | The amount of a salt that can dissolve in a solution, which varies depending on pH when the salt contains weak acid, weak base, or hydroxide ions. |
| weak acid | An acid that only partially ionizes in solution, establishing an equilibrium between the molecular form (HA) and its conjugate base (A-). |
| weak base | A base that only partially dissociates in water; examples include ammonia and carboxylate ions. |
| Term | Definition |
|---|---|
| complete ionization | The process where all molecules of a strong acid or base separate into ions in aqueous solution. |
| conjugate base | The species formed when an acid donates a proton; the base form in an acid-base conjugate pair. |
| hydronium ion | The aqueous ion H3O+(aq) formed when a hydrogen ion bonds with a water molecule; represents the form of hydrogen ion in aqueous solution. |
| hydroxide ion | The negatively charged ion OH− produced when water autoionizes or when a base dissolves in water. |
| ionize | The process by which a compound separates into ions when dissolved in solution. |
| pH | A logarithmic scale used to express the concentration of hydronium ions in a solution, calculated as −log[H3O+]. |
| pOH | A logarithmic scale used to express the concentration of hydroxide ions in a solution, calculated as −log[OH−]. |
| strong acid | An acid that completely dissociates in water and has a very weak conjugate base; examples include HCl, HBr, HI, HClO₄, H₂SO₄, and HNO₃. |
| strong base | A base that completely dissociates in water and has a very weak conjugate acid; group I and II hydroxides are common examples. |
| Term | Definition |
|---|---|
| conjugate acid | The species formed when a base accepts a proton; the acid form in an acid-base conjugate pair. |
| conjugate base | The species formed when an acid donates a proton; the base form in an acid-base conjugate pair. |
| equilibrium | The state in which the forward and reverse reaction rates are equal, resulting in constant concentrations or partial pressures of reactants and products. |
| hydronium ion | The aqueous ion H3O+(aq) formed when a hydrogen ion bonds with a water molecule; represents the form of hydrogen ion in aqueous solution. |
| hydroxide ion | The negatively charged ion OH− produced when water autoionizes or when a base dissolves in water. |
| ionization | The process by which an acid or base separates into ions when dissolved in water. |
| Ka | The acid ionization constant that expresses the equilibrium between a weak acid and its conjugate base in water. |
| Kb | The base ionization constant that expresses the equilibrium between a weak base and its conjugate acid in water. |
| Kw | The ion product constant for water, equal to [H3O+][OH−] = 1.0 × 10−14 at 25°C, representing the equilibrium constant for water autoionization. |
| monoprotic weak acid | An acid that can donate one proton and only partially ionizes in water, establishing an equilibrium between the molecular acid and its conjugate base. |
| monoprotic weak base | A base that can accept one proton and only partially ionizes in water, establishing an equilibrium between the molecular base and its conjugate acid. |
| percent ionization | The percentage of weak acid or base molecules that ionize in solution, calculated from the equilibrium concentration of ions and the initial concentration of the acid or base. |
| pH | A logarithmic scale used to express the concentration of hydronium ions in a solution, calculated as −log[H3O+]. |
| pKa | The negative logarithm of the acid dissociation constant (Ka); used to compare the relative strength of weak acids and predict protonation state at different pH values. |
| pKb | The negative logarithm of the base dissociation constant (Kb); used to compare the relative strength of weak bases. |
| pKw | The negative logarithm of Kw; equals 14.0 at 25°C and represents the sum of pH and pOH in any aqueous solution at that temperature. |
| pOH | A logarithmic scale used to express the concentration of hydroxide ions in a solution, calculated as −log[OH−]. |
| un-ionized | The molecular form of a weak acid or base that has not separated into ions in solution. |
| Term | Definition |
|---|---|
| buffer solution | A solution containing a large concentration of both members of a conjugate acid-base pair that resists changes in pH when small amounts of acid or base are added. |
| conjugate acid | The species formed when a base accepts a proton; the acid form in an acid-base conjugate pair. |
| conjugate base | The species formed when an acid donates a proton; the base form in an acid-base conjugate pair. |
| equilibrium constant | A numerical value that expresses the ratio of products to reactants at equilibrium, indicating the extent to which a reaction proceeds. |
| equimolar | Containing equal numbers of moles of two or more substances. |
| excess reagent | The reactant that remains after a reaction has gone to completion, with the other reactant being completely consumed. |
| Henderson-Hasselbalch equation | An equation used to calculate the pH of a buffer solution based on the pKa of the weak acid and the ratio of conjugate base to weak acid concentrations. |
| major species | The chemical species present in significant concentrations in a solution. |
| strong acid | An acid that completely dissociates in water and has a very weak conjugate base; examples include HCl, HBr, HI, HClO₄, H₂SO₄, and HNO₃. |
| strong base | A base that completely dissociates in water and has a very weak conjugate acid; group I and II hydroxides are common examples. |
| weak acid | An acid that only partially ionizes in solution, establishing an equilibrium between the molecular form (HA) and its conjugate base (A-). |
| weak base | A base that only partially dissociates in water; examples include ammonia and carboxylate ions. |
| Term | Definition |
|---|---|
| acidic protons | The protons in a polyprotic acid that can be donated to other species. |
| analyte | The substance in a solution whose amount or concentration is being determined during a titration. |
| conjugate acid | The species formed when a base accepts a proton; the acid form in an acid-base conjugate pair. |
| conjugate acid-base pair | Two species that differ by one proton, where one is the acid form and the other is the base form of the same substance. |
| conjugate base | The species formed when an acid donates a proton; the base form in an acid-base conjugate pair. |
| equivalence point | The point in a titration where the analyte is completely consumed by the titrant in a quantitative reaction. |
| half-equivalence point | The point in a titration halfway to the equivalence point, where the concentrations of a conjugate acid-base pair are equal. |
| monoprotic acid | An acid that can donate one proton (hydrogen ion) per molecule. |
| pKa | The negative logarithm of the acid dissociation constant (Ka); used to compare the relative strength of weak acids and predict protonation state at different pH values. |
| polyprotic acid | An acid that can donate more than one proton (hydrogen ion) per molecule. |
| proton-transfer reaction | A chemical reaction in which a proton is transferred from one species to another. |
| strong acid | An acid that completely dissociates in water and has a very weak conjugate base; examples include HCl, HBr, HI, HClO₄, H₂SO₄, and HNO₃. |
| strong base | A base that completely dissociates in water and has a very weak conjugate acid; group I and II hydroxides are common examples. |
| titrant | A solution of known concentration that is added to an analyte during a titration to determine the amount of analyte present. |
| titration | An analytical procedure used to determine the amount of an analyte in solution by reacting it with a titrant of known concentration. |
| titration curve | A graph plotting pH versus the volume of titrant added during a titration, used to summarize titration results. |
| weak acid | An acid that only partially ionizes in solution, establishing an equilibrium between the molecular form (HA) and its conjugate base (A-). |
| weak base | A base that only partially dissociates in water; examples include ammonia and carboxylate ions. |
| Term | Definition |
|---|---|
| acid strength | The ability of an acid to donate protons, determined by the stability of its conjugate base; stronger acids more readily donate protons. |
| base strength | The ability of a base to accept protons, determined by the stability of its conjugate acid; stronger bases more readily accept protons. |
| carboxylate ion | The conjugate base of a carboxylic acid, formed when a carboxylic acid donates a proton; a common weak base. |
| carboxylic acid | A class of weak organic acids containing a carboxyl group (-COOH) that can donate a proton. |
| conjugate acid | The species formed when a base accepts a proton; the acid form in an acid-base conjugate pair. |
| conjugate base | The species formed when an acid donates a proton; the base form in an acid-base conjugate pair. |
| electronegativity | A measure of an atom's ability to attract valence electrons in a chemical bond; increases across a period and decreases down a group in the periodic table. |
| inductive effect | The stabilization or destabilization of a conjugate base through the withdrawal or donation of electron density by nearby atoms or groups. |
| molecular structure | The arrangement of atoms and bonds in a molecule that determines its chemical properties and reactivity. |
| resonance | The representation of a molecule using two or more equivalent Lewis structures that differ only in the placement of electrons, used to describe bonding when a single structure is inadequate. |
| stabilization | The process by which structural features such as electronegativity, inductive effects, or resonance make a conjugate base or conjugate acid more stable and less likely to reform the original acid or base. |
| strong acid | An acid that completely dissociates in water and has a very weak conjugate base; examples include HCl, HBr, HI, HClO₄, H₂SO₄, and HNO₃. |
| strong base | A base that completely dissociates in water and has a very weak conjugate acid; group I and II hydroxides are common examples. |
| weak acid | An acid that only partially ionizes in solution, establishing an equilibrium between the molecular form (HA) and its conjugate base (A-). |
| weak base | A base that only partially dissociates in water; examples include ammonia and carboxylate ions. |
| Term | Definition |
|---|---|
| acid-base indicator | A substance that exhibits different observable properties (such as color) depending on its protonation state, allowing it to signal pH changes in a solution. |
| conjugate acid | The species formed when a base accepts a proton; the acid form in an acid-base conjugate pair. |
| conjugate base | The species formed when an acid donates a proton; the base form in an acid-base conjugate pair. |
| deprotonated | The state of a molecule or ion after it has donated a proton (H+), decreasing its positive charge or increasing its negative charge. |
| equivalence point | The point in a titration where the analyte is completely consumed by the titrant in a quantitative reaction. |
| pKa | The negative logarithm of the acid dissociation constant (Ka); used to compare the relative strength of weak acids and predict protonation state at different pH values. |
| pKb | The negative logarithm of the base dissociation constant (Kb); used to compare the relative strength of weak bases. |
| predominant form | The chemical species (protonated or deprotonated) that exists in higher concentration in solution at a given pH. |
| protonated | The state of a molecule or ion after it has accepted a proton (H+), increasing its positive charge or decreasing its negative charge. |
| protonation state | The relative concentrations of the protonated (HA) and deprotonated (A-) forms of an acid or base in solution. |
| titration | An analytical procedure used to determine the amount of an analyte in solution by reacting it with a titrant of known concentration. |
| weak acid | An acid that only partially ionizes in solution, establishing an equilibrium between the molecular form (HA) and its conjugate base (A-). |
| weak base | A base that only partially dissociates in water; examples include ammonia and carboxylate ions. |
| Term | Definition |
|---|---|
| buffer solution | A solution containing a large concentration of both members of a conjugate acid-base pair that resists changes in pH when small amounts of acid or base are added. |
| conjugate acid | The species formed when a base accepts a proton; the acid form in an acid-base conjugate pair. |
| conjugate acid-base pair | Two species that differ by one proton, where one is the acid form and the other is the base form of the same substance. |
| conjugate base | The species formed when an acid donates a proton; the base form in an acid-base conjugate pair. |
| pH stabilization | The ability of a buffer solution to maintain a relatively constant pH despite the addition of small amounts of acid or base. |
| Term | Definition |
|---|---|
| buffer solution | A solution containing a large concentration of both members of a conjugate acid-base pair that resists changes in pH when small amounts of acid or base are added. |
| concentration ratio | The ratio of the concentration of the conjugate base to the concentration of the conjugate acid, [A-]/[HA], in a buffer solution. |
| conjugate acid-base pair | Two species that differ by one proton, where one is the acid form and the other is the base form of the same substance. |
| dissociation | The process by which a compound breaks apart into its constituent ions or molecules in solution. |
| equilibrium expression | A mathematical equation that relates the concentrations or partial pressures of reactants and products at equilibrium, expressed as Kc or Kp. |
| pH | A logarithmic scale used to express the concentration of hydronium ions in a solution, calculated as −log[H3O+]. |
| pKa | The negative logarithm of the acid dissociation constant (Ka); used to compare the relative strength of weak acids and predict protonation state at different pH values. |
| weak acid | An acid that only partially ionizes in solution, establishing an equilibrium between the molecular form (HA) and its conjugate base (A-). |