Acids Bases & Redox

What is an acid

A proton donor (H+)

What’s a strong and weak acid

• strong acid fully ionises in water → higher conc of H+ ions

• weak acid partially ionises in water → lower conc of H+ ions

What is an alkali

• releases OH- ions in aqueous solutions

• soluble

What is a base

• A proton acceptor

• insoluble

• e.g. metal oxides, some metal hydroxides

What are the general equations with acids

• acid + base → salt + water (neutralisation)

• acid + metal oxide → salt + water

• acid + carbonate → salt + water + CO2

• acid + metal → salt + hydrogen

What is a salt

• when the hydrogen of the acid is replaced by a positive metal ion (cation)

What is the general ionic equation for neutralisation

H+ + OH- → H2O

What is an amphoteric solution?

• when something acts as both an acid and a base

• eg amino acids

What is oxidation and reduction

Oxidation: loss of electrons

Reduction: gain of electrons

What are rules for oxidation state

• must always add to 0 in compounds

• in ions, it must add to the charge number (eg add to -2 in SO4 2-)

• if it is a diatomic element, must divide by 2 to find oxidation state of each atom (eg in N2 must divide by 2)

• oxidation of a single element is always 0

• INCREASE in oxidation state = OXIDATION

• DECREASE in oxidation state = REDUCTION

What are oxidising and reducing agents

• oxidising agent: accepts/gain electrons but is REDUCED ITSELF

• reducing agents: donates/loses electrons but is OXIDISED ITSELF

In terms of oxidation what does it mean when a metal reacts with an acid to produce H2?

• metal is OXIDISED

• hydrogen is REDUCED