Buffers, Titrations, and Intermolecular Forces - Vocabulary

Vocabulary flashcards covering key concepts from buffers, titrations, polyprotic acids, and intermolecular forces discussed in the lecture.

Henderson-Hasselbalch equation

pH = pKa + log([base]/[acid]); used to calculate the pH of a buffer; requires both acid and conjugate base present; when [base] = [acid], pH = pKa.

Buffer

A solution that resists pH changes by containing a weak acid and its conjugate base (or weak base and conjugate acid), neutralizing added strong acid or base.

Buffer capacity

The amount of strong acid or base a buffer can neutralize before its buffering ability is overwhelmed; depends on buffer concentration.

Equimolar

Having equal molar concentrations of an acid and its conjugate base in a buffer.

pKa

The negative logarithm of Ka; the pH at which an acid is half dissociated; a property of the acid.

Equivalence point

The point in a titration at which the added titrant has exactly neutralized the analyte (stoichiometric completion).

Midpoint (titration)

The point halfway to equivalence; [acid] = [conjugate base]; pH = pKa at this point.

Equivalents

The amount of titrant required to completely titrate the analyte; the x-axis value at equivalence; multiple if the analyte has multiple removable protons.

Polyprotic acid

An acid that can donate more than one proton (e.g., H3PO4), with multiple deprotonation steps (Ka1, Ka2, Ka3).

pKa1, pKa2, pKa3

The pKa values corresponding to successive deprotonation steps of a polyprotic acid.

Buffer region

The pH range over which a buffer effectively resists pH changes; typically within ±1 pH unit of the pKa.

Acetic acid

A weak acid (CH3COOH) that forms its conjugate base acetate in solution.

Acetate

Conjugate base of acetic acid (CH3COO−).

Neutralization reaction

Acid-base reaction that produces water and a salt (e.g., CH3COOH + OH− → H2O + CH3COO−).

Titrant

The solution added from a burette to react with the analyte (e.g., NaOH in acid-base titrations).

Analyte

The substance being titrated in a titration experiment.

Hydrogen bond

A strong dipole-dipole interaction where a hydrogen covalently bonded to F, O, or N interacts with a lone pair on another electronegative atom.

Ion-dipole interaction

Attraction between an ion and a polar molecule, oriented to maximize electrostatic interaction.

Dipole-dipole interaction

Attraction between two polar molecules, maximizing alignment of opposite partial charges.

Ionic bond

Electrostatic attraction between oppositely charged ions; very strong, often called an ionic bond in solids.

Intermolecular forces

Forces between molecules, including ion-ion, ion-dipole, dipole-dipole, and hydrogen bonding.

Lone pair

A pair of nonbonding electrons on an atom that can participate in interactions such as hydrogen bonding.