Electrolytic processes Flashcards
describe the process of electrolysis
Breaking down ionic substances using electricity, forming useful elements or compounds
Describe the movement of ions during electrolysis
a) positively charged cations migrate to the negatively charged cathode, they gain electrons there and so are reduced
b) negatively charged anions migrate to the positively charged anode, they lose electrons there and so are oxidised
what does oxidation and reduction result in
oxidation = loss of electrons, reduction = gain of electrons
where does oxidation and reduction occur in electrolysis
reduction occurs at the cathode and that oxidation occurs at the anode in electrolysis reactions
what are the uses of sodium
Sodium is used in street lamps. A bright yellow light is given out when an electric current is passed through sodium vapour in the lamp. Liquid sodium has a high heat capacity. This makes it useful as a coolant in some nuclear power stations
Describe how the electrolysis of aqueous solutions can give products from ions in water, rather than from ions of the dissolved solid
in solution (water) there are h+ and OH- ions from water. at the anode the simplest ion is discharged. at the cathode a metal will be discharged if it is less reactive than hydrogen. if it is more reactive hydrogen will be discharged.
Describe the purification of copper by electrolysis using a pure copper cathode and an impure copper anode
cathode starts as a thin piece of pure copper and more pure copper and more pure copper adds to it. the anode is just a big lump of impure copper, which will dissolve. the electrical supply: pulls electrons of copper atoms at the anode, causing them to go into solution as Cu2+ ions. then offering electrons at the cathode to nearby Cu2+ ions to turn them back into copper atoms. the impurities are dropped at the anode as a sludge, whilst pure copper atoms bond to the cathode.
Explain how electroplating can be used
improves the appearance of metal objects and their resistance to corrosion. jewellery may be electroplated with silver or gold. galvanised steel is steel coated with a thin layer of zinc to improve its resistance to rusting.
what are electrolytes
electrolytes are ionic substances in the molten state
or dissolved in water
Explain the formation of the products in the electrolysis of
sodium chloride solution
at the cathode, two hydrogen ions accept one electron each to become on hydrogen molecule. at the anode two chloride ions lose one electron each and become one chlorine molecule.
Describe the manufacture of sodium by the electrolysis of molten sodium chloride
sodium is produced at the cathode and chlorine is produced at the anode. at the cathode, sodium ions are reduced to become sodium atoms. at the anode, chloride ions are oxidised and pair up to form chlorine molecules. sodium can be collected from the cathode
describe how electroplating is carried out
the cathode is the object to be electroplated. the anode is the plating metal. the electrolyte contains ions of the plating metal. during electroplating, ions form the electrolyte move to the object and are discharged as metal atoms. they are replaced by ions leaving the anode.
