Oxidation, reduction and redox equations

Examples of acids

Weak acids partially dissociate

HCl- hydrochloric acid

H2SO4- sulfuric acid

HNO3- nitric acid

CH3COOH- ethanoic acid

All contain hydrogen, when you dissolve an acid in water, the hydrogen is released as the hydrogen ion H+ (proton)

Examples of bases

Base can neutralise an acid to produce a salt

CuO- copper oxide

Mg(OH)2- magnesium hydroxide

Na2CO3- sodium carbonate

NH3- ammonia

Neutralisation reaction

Metal oxide + acid → salt + water

Metal hydroxide + acid → salt + water

Metal carbonate + acid → salt + carbon dioxide + water

Alkalis

Bases that dissolve in water, in solution release hydroxide ions OH-

All group 1 metal hydroxides are soluble in water and can form alkalis

Ammonia and water

Ammonia + water → ammonium hydroxide

NH3 + H2O → NH4OH

Oxidation and reduction

Oxidation Is Loss of electrons (and removal of hydrogen) but gain in oxygen

Reduction Is Gain of electrons (and addition of hydrogen) but loss in oxygen

Spectator ions are ions that don’t change

Reducing agent

• gets oxidised

• Causes something else to be reduced

• Donates (loses) electrons

Mg → Mg 2+ + 2e-

Oxidising agent

• gets reduced

• Causes something else to be oxidised

• Accepts (gains) electrons

Zn 2+ + 2e- → Zn

Oxidation states

How electrons are lost or gained in a reaction

MgO

Mg 2+ oxidation number is +2

O 2- oxidation number is -2