Rossita Radzak: SASER

ELECTROCHEMISTRY 1. Factor that affect the electrolysis of an aqueous solution

(a) position of ions in the electrochemical series (cathode) (b) Anode :concentration of ions in the electrolyte - halogen ( Chloride, bromide and

iodide) (c) Anode : type of electrodes used in the electrolysis – ( anode – metal )

Application (i) Electroplating

anode – electroplating metal ( less electropositive metal / Cu, Ag, Ni ) cathode – metal /object to be electroplated electrolyte - solution that contains the metal ions of electroplating metal

(ii) Purification

anode – impure metal ( Cu Cu2+ + 2e )

cathode –pure metal ( Cu2+ + 2e Cu ) electrolyte - solution that contains the metal ions

(iii) Extraction of metal (reactive metal, sodium, aluminium)

Down`s Process – extraction of sodium from molten sodium chloride. Extraction of aluminium from molten aluminium oxide ( bauxite)

2. To construct the electrochemistry based on: (i) tendency to release electron / potential differences - voltaic cell.

(ii) ability / tendency of metal to displace another metal from it salts solution – displacement reaction.

Rossita Radzak: SASER

Cell P Cell Q Compare and contrast cell P and Q. Include in your answer the observation and half equation for the reaction of the electrodes in both cells.

Cell P Characteristics Cell Q Electrical chemical Energy change Chemical electrical +ve / anode: copper -ve / cathode: copper

Electrode +ve/cathode: copper -ve/ anode: lead

Cu2+ , H+

OH- , SO42-

Ions present in the electrolyte

Cu2+ , H+

OH- , SO42-

Anode :Cu Cu2+ + 2e Cathode: Cu2+ + 2e Cu

Half equation Anode: Pb Pb2+ + 2e Cathode: Cu2+ + 2e Cu

Anode: copper electrode become thinner Cathode: brown solid formed/ becomes thicker. Electrolyte: intensity blue solution / concentration of solution remain

Observation Anode: becomes thinner Cathode: becomes thicker / brown solid formed Electrolyte: intensity blue solution decrease / blue becomes paler

copper Copper(II) sulphate solution

lead