Acid-Base Concepts, Reactions, and pH Scale

Flashcards covering key vocabulary from Acid-Base Concepts, Reactions of Acids and Bases, and The pH Scale lectures.

Acid

A compound or ion that donates protons (H+ ions).

Base

A compound or ion that accepts protons (H+ ions).

Proton

Another name for a hydrogen ion (H+).

Hydronium ion

Formed when a proton bonds with unpaired electrons in water (H3O+).

Coordinate bond

A highly polarised bond where one atom (e.g., oxygen in water) provides both electrons for the shared pair.

Equilibrium (⇌)

A state where the forward reaction does not go to completion, and a backward reaction continually occurs.

Amphiprotic

A substance that can both donate and accept protons (e.g., water, hydrogen carbonate ion).

Amphoteric

A substance that can act both as an acid and as a base (e.g., water, certain metal oxides).

Strong acid/base

An acid or base that undergoes complete ionisation in water.

Weak acid/base

An acid or base that only partially ionises in water.

Brønsted Lowry theory

Describes acid-base reactions as the transfer of a proton, where an acid forms its conjugate base and a base forms its conjugate acid.

Conjugate pair

Two species that differ by a single proton (H+).

Monoprotic acid

An acid that can donate only one proton (e.g., HCl).

Polyprotic acid

An acid that can donate more than one proton (e.g., H2SO4, H3PO4).

Diprotic acid

A polyprotic acid that can donate two protons (e.g., H2SO4).

Triprotic acid

A polyprotic acid that can donate three protons (e.g., H3PO4).

Acid-base indicator

A weak acid or base where the acidic form has a different color from the basic form, used to signal the endpoint of a titration.

Neutralisation

Reactions between acids and bases, typically forming a salt and water, and often releasing heat (exothermic).

Basic metal oxide

A metal oxide that reacts with water to form hydroxide ions and with acids to form a salt and water.

Acidic non-metal oxide

A non-metal oxide that reacts with water to form an acid and with bases to form a salt and water.

Titration

A volumetric analysis procedure used to determine the concentration of an unknown solution.

Analyte

The solution with an unknown concentration in a titration.

Titrant

A solution of known concentration used to react with the analyte in a titration.

Equivalence point

The exact point in a titration where the moles of acid and base (H3O+ and OH-) are stoichiometrically equivalent.

Endpoint

The point in a titration where the indicator permanently changes color, providing an estimation of the equivalence point.

pH scale

A logarithmic scale that describes the concentration of hydronium ions ([H3O+]) in aqueous solutions, ranging from acidic (pH < 7) to basic (pH > 7) with neutral at pH 7.

pH equation

pH = -log[H3O+], used to calculate pH from hydronium ion concentration.

Water ion product constant (Kw)

Kw = [OH-].[H3O+] = 1 x 10^-14, representing the equilibrium constant for water autoionization.

Acid rain

Rain with a pH below 5.6, caused by atmospheric oxides of sulfur and nitrogen reacting with water to form strong acids.

Sulfur dioxide (SO2)

An acidic oxide produced from burning sulfur-containing fossil fuels, which reacts with water to form sulfurous acid.

Sulfur trioxide (SO3)

An acidic oxide formed from sulfur dioxide and oxygen, which reacts with water to form sulfuric acid.

Nitrogen oxides (NOx)

Gases like nitric oxide (NO) and nitrogen dioxide (NO2) formed at high temperatures (e.g., in combustion engines), contributing to acid rain.