Acids and Bases Basics - Vocabulary Flashcards

Vocabulary-style flashcards covering key concepts, definitions, and relationships from acids and bases basics.

Acid (Arrhenius definition)

A substance that releases H+ ions in aqueous solution, forming hydronium (H3O+).

Base (Arrhenius definition)

A substance that releases OH− ions in aqueous solution.

Bronsted-Lowry acid

A substance that donates a proton (H+).

Bronsted-Lowry base

A substance that accepts a proton (H+).

Conjugate acid

The species formed when a base accepts a proton (e.g., H2O becomes H3O+).

Conjugate base

The species formed when an acid donates a proton (e.g., HCl → Cl−).

Amphoteric

A substance that can behave as an acid or a base depending on the reaction (e.g., water, H2PO4−).

Hydronium ion

H3O+, the hydrated proton produced when acids donate H+ to water.

Hydroxide ion

OH−, the base produced in many acid–base reactions.

Kw (autoionization of water)

The equilibrium constant for water self-ionization: Kw = [H3O+][OH−] ≈ 1.0×10−14 at 25°C; temperature dependent.

pH

Negative log of [H3O+]; pH + pOH ≈ 14 at 25°C; acidic solutions have pH < 7, basic solutions > 7.

pOH

Negative log of [OH−]; related to pH by pH + pOH ≈ 14 at 25°C.

Ka

Acid dissociation constant for HA + H2O ⇌ H3O+ + A−; larger Ka means a stronger acid.

Kb

Base dissociation constant for B + H2O ⇌ BH+ + OH−; larger Kb means a stronger base.

pKa

Negative log of Ka; lower pKa indicates a stronger acid; for conjugate pairs, pKa + pKb = pKw (≈14 at 25°C).

pKb

Negative log of Kb; relates to pKa by pKa + pKb = pKw.

Strong acid

An acid that ionizes nearly completely in water; strong electrolytes (examples: HCl, HBr, HI, HNO3, H2SO4, HClO4; HF is a weak acid).

Weak acid

An acid that partially ionizes in water (equilibrium; examples: HF, acetic acid, HNO2, HSO3−, NH4+).

Strong base

A base that dissociates completely in water; typically soluble hydroxides (examples: NaOH, KOH, Ba(OH)2).

Weak base

A base that dissociates only partially in water; examples: NH3, F−, NO2−, CH3COO−, CN−, HSO3−.

Oxyacid acidity trend

For oxyacids, more oxygen atoms generally means a stronger acid (e.g., HClO4 > HClO3 > HClO2); HCl is not an oxyacid and may not follow this trend.

Lewis acid

Electron pair acceptor (example: AlCl3 accepts electrons from NH3).

Lewis base

Electron pair donor (example: NH3 donates lone pair to AlCl3).

Neutral salt

A salt that yields a solution with pH ≈ 7 (e.g., NaCl in water).

Conjugate base of HF

F−; formed when HF donates a proton.

Conjugate acid of NH3

NH4+; formed when NH3 accepts a proton.

Amphoteric examples

Water and H2PO4− can act as either acid or base depending on the reaction.

Self-ionization of water reaction

2 H2O ⇌ H3O+ + OH−; Kw = 1.0×10−14 at 25°C; temperature dependent.