REVISION ELECTROCHEMISTRY

REDUCTION CATHODE Reduction is a gain of electrons The oxidation number decreases E.g. Electrodes where reduction take place will increase in mass We write the reduction reaction ‘right-way-round’ from the table Oxidising agent CATHODE The electrode where reduction takes place

OXIDATION ANODE Oxidation is a loss of electrons The oxidation number increases E.g. Electrodes where oxidation take place will reduce in mass We write the oxidation reaction ‘upside-down’ from the table Reducing agent ANODE The electrode where oxidation takes place

ELECTROLYTE solution/liquid/dissolved substance that conducts electricity through the movement of ions.

OXIDATION NUMBERS (p23) OXIDATION RULES fluorine is always -1 The rest of the halogens chlorine, bromine and iodine usually -1, unless they bind with oxygen or fluorine - then we will have to work out their oxidation numbers Hydrogen is usually +1 unless it binds with a metal, then it is -1 OXYGEN is usually -2, except it is -1 in H2O2 and O22- and +1 if it binds with fluorine Group 1 is always +1 Group 2 is always +2 The most electronegative element always has the negative oxidation number Neutral diatomic molecules such as H2 and Cl2's oxidation number is 0 Isolated ions’ oxidation number is equal to the charge according to the periodic table OXIDATION NUMBERS (p23)