electrolysis

Question 1

what is electrolysis?

Answer 1

electrolysis is the splitting up of an ionic substance using electricity

Question 2

what will form at the posititve electrode?

Answer 2

at the positive electrode (anode) oxygen is produced unless the solution contains halide ions (fluoride, bromine, chloride, iodide) then the halogen is produced (fluorine, bromine, iodine, chlorine)

Question 3

what forms at the negative electrode?

Answer 3

at the negative electrode (cathode) hydrogen is produced if the metal is MORE reactive than hydrogen otherwise the metal is produced

Question 4

what are the two methods of electrolysis in ionic compounds?

Answer 4

molten
aqueous solution

Question 5

why does electrolysis only work on ionic substances?

Answer 5

because in order for electrolysis to work you need ions

Question 6

why does electrolysis not work in solids?

Answer 6

the ions are fixed so cannot move

Question 7

what is the process of electrolysis?

Answer 7

once the electrodes are in the ionic substance and the current is turned on the ions are pulled to the oppositely charged electrode.
the ions are then oxidised or reduced and turn back to atoms

Question 8

what is the gaining of electrons called?

Answer 8

reduction

Question 9

what is it called when an ion loses electrons?

Answer 9

oxidation

Question 10

what is the only type of substance that electrolysis works on?

Answer 10

ionic substances

Question 11

what are the positive and negative electrodes called?

Answer 11

the positive electrode is called the anode
the negative electrode is called the cathode

PANIC

Question 12

what is the process of electrolysis with water?

Answer 12

water splits up into H+ ions and OH- ions
OH- is attracted to the positive elctrode H+ is attracted to the negative
OH- is oxidised and oxygen is formed

Question 13

what are electrodes made from?

Answer 13

carrbon

Question 14

how can you remove a metal from its metal oxide compund?
whats the word equation

Answer 14

reduction with carbon

metal oxide+ carbon —-> metal + carbon dioxide

Question 15

what determines whether a metal can be extrected by the reduction of carbon or not?

Answer 15

its place in the reactivity series
if it more reactive than carbon then it will have to be extracted using electrolysis however if its less reactive thann carbon then it can be

Question 16

if a metal in the ground is found by itself what does it mean about that metal?

Answer 16

it is extremely unreactive

Question 17

give an example of a redox reaction

Answer 17

displacement reactions

Question 18

what is a redox reaction?

Answer 18

a reaction where electrons are transfered

Question 19

what is the solution that is being seperated called?

Answer 19

the electrolyte

Question 20

why is alluminium mixed with cryolite during its electrolysis?

Answer 20

to lower its boiling point

Question 21

what are the half equations for alluminium and oxygen during there electrolysis?

Answer 21

Al 3+ + 3e- —-> Al

2O 2- —–> O2 + 4e-

Question 22

whats different about electrolysing an aqueous solution?

Answer 22

you have to factor in the water ions as well

Question 23

what is produced at the negative cathode if an AQUEOUS solution is electrolysed?

Answer 23

hydrogen is produced if the metal is more reactive than hydrogen

Question 24

what is made at the anode during the electrolysis of AQUEOUS solutions?

Answer 24

oxygen is produced unless halgoens are present then they will be produced

Question 25

what is the half equation for the production of oxygen at the positive anode and a halide ion is not present?

Answer 25

4OH- -------> O2 + 2H2O + 4e- or 4OH- -4e- ---> O2 + 2H2O

Question 26

what is the process of extracting alluminium ore with electrolysis

Answer 26

alluminium is extracted from the ore bauxite, which contains alluminium oxide, by electrolysis alluminium oxide has a very hig melting point so cryolite is added to lower it. its now a molten MIXTURE which cintains ions that are free to move so will conduct electricity Al 3+ ions are attracted to the negative electrode and are reduced and O2- ions are attracted to the positive cathode and are oxidised

Question 27

what are the half equations at the positive and negative electrodes for the electrolysis of alluminium oxide?

Answer 27

positive- 2O 2- -----> O2 + 4e- negative- Al 3+ + 3e- ---> Al

Question 28

what is the half equation at the anode when a halide isn't present?

Answer 28

4OH- -----> O 2 + 2H2O + 4e-

Question 29

what is the half equation at the negative and positive electrodes for the electrolysis of sodium chloride?

Answer 29

negative : 2H+ + 2e- --------> H2 positive: 2Cl -------> Cl2 + 2e-

Question 30

what are some negatives about using electrolysis to extract metals?

Answer 30

it can be very expensive as it requires lots of energy