ES 3 Flashcards
(10 cards)
where does oxidation and reduction occur in electrolysis
oxidation occurs and the anode
reduction occurs at the cathode (red cat = reduction cathode)
where do anions and cations move during electrolysis
anions (-) move to the anode (+)
cations (+) move to the cathode (-)
what is always produced at the anode and the cathode
anode - non-metals (apart from hydrogen)
cathode - metal
what is the definition of electrolysis
electricity is passed through a molten or aqueous ionic compound and the compound is broken down meaning cations can move to the cathode and the anions can move to the anode. electrons are lost at the positive anode and gained at the negative cathode.
what happens during reduction at the cathode
will be metal ions from the salt and water
more reactive metals from group 1 and 2 remain as ions
hydrogen gas is produced from the reduction of water
less reactive metal will be deposited onto the cathode
what happens during oxidation at the anode
will be negative ions from the salt and water
halides have greater tendency to be oxidised than water so the halogen is produced at the anode
negative ions have less tendency to be oxidised than water so oxygen gas will be produced at the anode
what are electrodes usually made of
unreactive materials e.g. platinum and graphite
why is the anode and ions in solution sometimes the same e.g. copper
to purify metals or for metal plating
what is the anodes role in electroplating
sacrificial metal which is used for plating e.g. silver or copper (oxidation of the metal into ions in the solution)
anode decreases in mass since it is loosing ions to the cathode
what is the role of the cathode in electroplating
it is the object to be plated and reduction of the metal ions occurs and ions are plated onto the cathode)
cathode increases in mass since it is gaining ions from the anode
