Electrolysis

Question 1

what is electrolysis

Answer 1

the break down of ionic compounds into their elemental form

Question 2

what is an electrolyte

Answer 2

a liquid or solution containing ions

Question 3

why does the solution in electrolysis have to be a liquid

Answer 3

so the ions can freely move and carry electrical charge

Question 4

what happens at the anode and what happens at the cathode

Answer 4

anode - oxidation
cathode - reduction

Question 5

what happens when the negative ions reach the anode

Answer 5

the negative ions are discharged (lose their ions and become neutral) which cause them to pair up and float off

Question 6

what happens when the positive ions reach the cathode

Answer 6

the positive ions are discharged this causes the to form pure metals and sink to the bottom

Question 7

the metal is more reactive than hydrogen but is in an AQUEOUS SOLUTION

which one is discharged hydrogen or the metal

Answer 7

hydrogen

Question 8

the metal is more reactive than hydrogen but is in a liquid

which one is discharged hydrogen or the metal

Answer 8

the metal

Question 9

what are always discharged at the anode

Answer 9

halide ions

Question 10

if the halide ions are not discharge what are discharged instead

Answer 10

OH ions or hydroxide ions

Question 11

half equation for water from hydroxide ions

Answer 11

4OH –> 02 + H20 + 4e-

Question 12

how do we purify aluminium

Answer 12

to purify aluminium we have to make it into a molten so it can carry an electrical charge

Question 13

steps on making aluminium a molten

Answer 13

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

Question 14

what is formed at the cathode in the electrolysis of aluminium oxide and why

Answer 14

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

Question 15

what is formed at the anode in the electrolysis of aluminium oxide and why

Answer 15

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

Question 16

disadvantage of electrolysis

Answer 16

it requires a lot of energy and is expensive

Question 17

what would you have to do for electrolysis to occur in insoluble substances

Answer 17

melt the substances

Question 18

what would you have to do for electrolysis to occur in soluble substances

Answer 18

dissolve the substances in water (to produce an aqueous solution)

Question 19

method for the electrolysis of copper chloride
REQUIRED PRACTICAL

Answer 19

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

Question 20

how do you prove the presence of chlorine gas

Answer 20

litmus paper
will turn blue to a bleached colour

Question 21

method for the electrolysis of sodium chloride REQUIRED PRACTICAL

Answer 21

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

Question 22

how to test for hydrogen

Answer 22

the squeaky pop test
you would collect hydrogen and light it and if hydrogen is present it will squeak

Question 23

hazard of the REQUIRD PRACTICALS

Answer 23

• 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

Question 24

anomalies of the required practical

Answer 24

• gas escapes
• change in voltage
• change in temperature

Question 25

what is brine

Answer 25

concentrated sodium chloride

Question 26

uses of the chlorine in brine

Answer 26

cleaning products and to kill bacteria

Question 27

uses for the sodium hydroxide in brine

Answer 27

• oven cleaners
• to unblock drains

Question 28

products in brine

Answer 28

• chlorine
• hydrogen
• sodium hydroxide

Question 29

brine decomposition

Answer 29

2NaCl + 2H2O —> 2NaOH + H2 + Cl2

Question 30

what is electroplating

Answer 30

the process where metal atoms are transported onto the surface of other metal using electricity

Question 31

what is electroplating used for

Answer 31

• aesthetics e.g jewellery
• protection

Question 32

what goes to the anode in electroplating

Answer 32

the metal used for plating

Question 33

what goes to the cathode in electroplating

Answer 33

the metal that is going to be plated