Electrolysis Flashcards
What is electrolysis
when a molten of aqueous ionic compound is decomposed using and electric current
why cant covalent compounds undergo electrolysis
because they do not conduct electricity
what is an Anode
a positive electrode
what is a cathode
negative electode
what is a anion
negatively charged ion anode
what is a cation
positively charged ion attracted to cathode
how does electrons flow in electrolytic cell
from anode to cathode
what do aqueous solution have that contribute to electrolysis
water that spilt into H+ and OH- ions
Explain what occurs in the cathode
- H+- and Metal ions are attracted to the cathode
- product form is dependant on reactivity series
is metal is more reactive than hydrogen then hydrogen is formed (bubbling) - exceptions copper silver gold
What happens in the anode
- OH- and non metal ions are attracted to the anode
- product formed is dependant how ion is discharged
- at anode oxygen is present unless metal ion is a halide.
explain the products of acidified water
hydrogen ion at cathode and oxygen at anode
what is a binary ionic compound
two element joined together by ionic bonding and when they are melted they can conduct electricity and carry a charge
explain the electrolysis of lead bromide
- what are the ions present
- what ions go where
- what is reduced and oxidised
- what can u observe
- ions present are Pb+ and H+ / OH- and Br-
- Pb+ and H+ ions are attracted to the cathode
- Pb is reduced as it is less reactive than hydrogen
- grey lead deposit at bottom of electrode
- OH- and Br- is attracted to the anode
- Br- is oxidised as it is a halide ion
- Brown vapour is given off by the bromide
how can you predict an electrolysis reaction of molten ionic compounds
at cathode metals are always formed and at anode non metal always formed
what are the results of the electrolysis of copper sulphate
copper is formed at the cathode as copper is less reactive than hydrogen and oxygen gas is produced at the anode as halide ions are not present
what is the method of electrolysis with inert electrodes
- pour copper sulfate into beaker
- place graphite rods attaching to opposite terminals
- fill two small tubes with copper sulfate and position over electrodes
- test gas produced using glowing splint and burning splint
Explain the method of electrolysis with copper electrodes
- pour copper sulfate in beaker
- measure mass of copper foil and attach to negative and positive end of terminal and dip into copper sulfate
- adjust power station and leave it for 30mins
- remove electrodes and dry so results accurate
what are we recording in the copper electrode experiment
change in mass of electrodes and currents used
what are recording in the inert electrode experiment
results of gas test and what is produced at each electrode
results of copper electrode: why is there a mass change
because copper is oxidised at anode and reduced at cathode therefore anode decreases in mass and cathode increases in mass as anode passes on copper to cathode
results copper electrode: why is mass constant
as copper deposited at negative electrode is the same as the copper lost from positive electrode
how is copper purified
copper is extracted from its ore using reduction by carbon then go through electrolysis to purify it using copper electrodes
what does the … look like at the start of purifying copper
1) anode
2) cathode
3) electrolyte
1) big lump of impure copper
2) copper sulfate solution ( Cu+)
3) cathode contains thin piece of pure copper
what happens during the process of electrolysis or purifying copper
impure copper at anode is oxidised and dissolves with electrolyte to form copper ions then the copper ions are reduced at the copper cathode and the layer of pure copper gets thicker any impurities sink to the bottom forming a sludge
what is the slude
highly valuable material that is refined as it contains small precious metals
