Electrolysis Flashcards
what is electrolysis
the break down of ionic compounds into their elemental form
what is an electrolyte
a liquid or solution containing ions
why does the solution in electrolysis have to be a liquid
so the ions can freely move and carry electrical charge
what happens at the anode and what happens at the cathode
anode - oxidation
cathode - reduction
what happens when the negative ions reach the anode
the negative ions are discharged (lose their ions and become neutral) which cause them to pair up and float off
what happens when the positive ions reach the cathode
the positive ions are discharged this causes the to form pure metals and sink to the bottom
the metal is more reactive than hydrogen but is in an AQUEOUS SOLUTION
which one is discharged hydrogen or the metal
hydrogen
the metal is more reactive than hydrogen but is in a liquid
which one is discharged hydrogen or the metal
the metal
what are always discharged at the anode
halide ions
if the halide ions are not discharge what are discharged instead
OH ions or hydroxide ions
half equation for water from hydroxide ions
4OH –> 02 + H20 + 4e-
how do we purify aluminium
to purify aluminium we have to make it into a molten so it can carry an electrical charge
steps on making aluminium a molten
1) we extract the pure aluminium from the bauxite
2) we mix the aluminium with the cryolite to lower the melting point, as aluminium has a high melting point so it would require a lot of energy for it to become a molten
3) then we melt the aluminium to form aluminium oxide which we use in electrolysis to form aluminium
what is formed at the cathode in the electrolysis of aluminium oxide and why
Aluminium is formed at the cathode as the aluminium ions are attracted to the cathode and are reduced. This makes them gain electrons and join together to form molten aluminium metal
what is formed at the anode in the electrolysis of aluminium oxide and why
Oxygen is formed at the anode as the oxygen ions are attracted to the anode and are oxidised. This makes the gain electrons and join together to float off as oxygen atoms
disadvantage of electrolysis
it requires a lot of energy and is expensive
what would you have to do for electrolysis to occur in insoluble substances
melt the substances
what would you have to do for electrolysis to occur in soluble substances
dissolve the substances in water (to produce an aqueous solution)
method for the electrolysis of copper chloride
REQUIRED PRACTICAL
1) add 50cm3 of copper chloride to the beaker
2) you would cover the beaker with a lid so the chlorine gas does not escape (to reduce a persons exposure time) since its very toxic
3) at the negative electrode we would see the copper accumulate on it as it has been discharged instead of hydrogen
4) at the positive electrode we would see bubbles of chlorine gas
how do you prove the presence of chlorine gas
litmus paper
will turn blue to a bleached colour
method for the electrolysis of sodium chloride REQUIRED PRACTICAL
1) add 50cm3 of sodium chloride into the beaker
2) you would cover the beaker with a lid so the chlorine gas does not escape (to reduce a persons exposure time) since its very toxic
3) at the cathode you would see hydrogen gas
4) at the anode chlorine gas is produced
how to test for hydrogen
the squeaky pop test
you would collect hydrogen and light it and if hydrogen is present it will squeak
hazard of the REQUIRD PRACTICALS
- you should have the room well ventilated as chlorine gas is toxic and the experiment should be carried at a short period of time to prevent high levels of chlorine
- low voltage to prevent electric shock
anomalies of the required practical
- gas escapes
- change in voltage
- change in temperature
