4. mole concept

simplest formula showing the ratio of the atoms of different elements in a compound.

Formula which shows the actual number of atoms each element in one molecule of the compound.

An acid is anything that dissociates in water to form H30+.
A base is anything that dissociates in water to form OH-.

e.g., HCl (g) + H2O (l) -> H3O+ + Cl-
e.g., NaOH (aq) -> Na+ (aq) + OH- (aq)

limitation: restricted to aqueous solutions

An acid is any species which donates a proton (H+)
A base is any species which accepts a proton (H+)

A Bronsted-Lowry reaction involves transfer of a proton from an acid to a base.

e.g., HCl (g) + NH3 (g) -> NH4Cl (s)

limitations: does not explain why substances like BF3 or AlCl3 behave like acids despite not containing any H atom.

An acid is any species that accepts an electron pair
A base is any species that receives an electron pair

A lewis acid-base reaction is the transfer of a pair of electrons from the base to the acid.
e.g., BF3 + NH3 -> BF3·NH3

limitations: too general

A reaction that simultaneously involves reduction and oxidation

A process where a substance gains electrons, resulting in a decrease in its oxidation state

A process where a substance loses electrons, resulting in an increase in oxidation state

A substance that gives electrons to another, itself becoming oxidised in the process.

A substance that receives electrons from another, itself becoming reduced in the process

A substance that is simultaneously oxidised and reduced in the same reaction

the total number of electrons that an atom either gains or loses in order to form a chemical bond with another atom