Electrolysis Flashcards
what is the literal definition of electrolysis
splitting up with electricity
anode
positive electrode
cathode
negative electrode
electrolyte
liquid or solution containing an ionic compound which allow for ions to freely move
purpose of battery in electrolysis
passes electric current from anode to cathode
when ions reach the electrode they are…
discharged(become a neutral atom)
oxidisation is
losing electrons
reduction is
gaining electrons
half equation at anode (positive electrode):
negative ion —> neutral atom + electron(s)
half equation at cathode:
positive ion + electron(s) —> neutral atom
electrolysis is using (long definition)…
electricity to convert ions in a compound into neutral atoms by transferring electrons from negatively charged ions to positively charged ions
metals often exist as
oxides
to get pure metals from metal oxides we have to
remove oxygen
cheapest removal of oxygen from metal oxides
using carbon to displace metal
what is the drawback of using carbon to displace metal in metal oxides
very few metals are less reactive than carbon, the rest are not displaced
what are the elements less reactive than carbon on the reactivity scale?
zinc, iron, hydrogen, copper
electrolysis is expensive because it
requires a lot of energy to melt metal oxides
electrolysis only works if ions can
move
what must metal oxides be for electrolysis to occur
molten (electrolyte)
metal oxides have very high melting points, what do we mix them with to lower the melting point
cryolite
what does cryolite do?
lowers the melting point of metal oxides
soluble solutions can be
dissolved in water to form an electrolyte
in aqueous solutions, ions from compounds are present as well as
ions from water: H+ and OH-
in solution, water splits into its ions:
H20 —> H+ + OH-
what is the rule for the cathode in aqueous electrolysis
hydrogen is always discharged unless copper is present
what is the rule for the anode in aqueous electrolysis
hydroxide always discharged unless Group 7 ion is present
Steps to the aqueous electrolysis RPA
- add 50cm^3 of first aqueous solution to a beaker with two inert electrodes that are not touching
- connect the electrodes to a power supply
- completely fill two test tubes with the first aqueous solution and position one over each of the electrodes
- turn on the power supply
- Any gases produced can be collected in the test tubes and tested e.g. litmus paper test for acid or alkali or squeaky pop test for hydrogen
- clean apparatuses and collect a new set of electrodes to repeat experiment with second aqueous solution
