Chemistry 3.6 (Aqueous Systems)

Terminology for NCEA Level 3 chemistry externals

Acid

Acid

A substance that donates a proton in solution, forming hydronium

Base

A substance that accepts a proton in solution, forming hydroxide

Strong acid

An acid that fully dissociates into ions in solution

Strong base

A base that fully dissociates into ions in solution

Weak acid

An acid that only partially dissolves into ions in solution

Weak base

A base that only partially dissolves into ions in solution

Equilibrium

When a reaction does not go to completion, rate of forward and backward reactions are equal

Solubility

The measure of how much substance dissolves

Solubility constant

Ks

Alkali

A base that is soluble

pH

Measure of the acidity or alkalinity of a solution

Hydronium

$H_3O^+$ ions, formed from an acid in solution

Hydroxide

$OH^-$ ions, formed from a base in solution

Salt

Formed when an acid and base react

Ionic product

The product of the concentrations of ions present

Precipitate

An insoluble solid suspended in solution

A precipitate forms when…

IP>Ks

Common ion effect

Solubility decreases when a common ion is present

Hydrobromic acid

$HBr$, a strong acid

Hydrochloric acid

$HCl$, a strong acid

Nitric acid

$HNO_3$, a strong acid

Sulphuric acid

$H_2SO_4$, a strong acid

Ethanoic acid

$CH_3COOH$, a weak acid

Hydrofluoric acid

$HF$, a weak acid

Ammonium

$NH_4^+$, a weak acid

Potassium hydroxide

$KOH$, a strong base

Sodium hydroxide

$NaOH$, a strong base

Ammonia

$NH_3$, a weak base

Ethanoate

$CH_3COO^-$, a weak base

Methylamine

$CH_3NH_2$, a weak base

Solvent

The substance that dissolves the solute

Solute

The substance that is dissolved in the solvent

Sparingly soluble

Very little of the substance dissolves

Equilibrium constant

Kc

Monoprotic

A substance that can only donate or accept one proton

Diprotic

A substance that can accept or donate two protons

Amphiprotic

A substance that can either donate or accept protons

Conjugate acid

Formed when a base donates a proton

Conjugate base

Formed when an acid accepts a proton

Conductivity

A measure of how strongly a substance can conduct electricity. Free ions or electrons must be present in order to conduct electricity

Electrolyte

Solution that contains ions and can conduct electricity

Acidity constant

Ka

Base constant

Kb

Ionic product of water

Kw

Relationship between Ka and Kb

Kw = Ka x Kb

Titration

Gradual addition of a substance of known concentration to a substance of unknown concentration to determine concentration

Titration curve

Plot of pH versus volume as a titration takes place

Equivalence point

Point where equivalent amounts of solutions have been added. In strong acid/strong base titrations, the base and acid would neutralise at the equivalence point

Buffer zone

Region where pH remains constant

Buffer solution

Substance that resists changes in pH

Acid salt

A salt that donates a proton to form hydronium ions in solution

Base salt

A salt that accepts a proton, forming hydroxide in solution.

pKa=pH

[acid]=[base]

pKa>pH

[acid]<[base]

pKa<pH

[acid]>[base]