Electrolytic Process

Question 1

Describe the reactions at the electrodes.

Answer 1

At the cathode electrons are transferred from the electrode to the positive ions at the an ode negative ions lose electrons. When positive ions gain electrons we call it reduction.

Question 2

What is an electrolyte

Answer 2

Something that conducts electricity it is used in electrolysis

Question 3

In molten electrolysis describe how metals and there partner are formed I.e sodium chloride

Answer 3

Oxidation is the loss of electrons reduction is the addition of electrons.
At the Anode negative ions are attracted to it, these ions are then oxidised as they are negative they then form an atom I.e Cl- to Cl2
At the cathode electrons from the anode are used to reduce the positive atoms I.e Na+ + E- to Na

Question 4

Why is copper always formed at the cathode?

Answer 4

Because copper is positive therefore attracts to the negative anode where is it reduced.

Question 5

What happens in electrolysis when water is used as the solute and the salt is dissolved

Answer 5

If the salt is more reactive than hydrogen it will form at the cathode however if it is less reactive then water it will form at the bottom of the container and the hydrogen will be found at the cathode.

Question 6

Describe advantages of electro plating

Answer 6

Makes things look nicer, I.e gold plating

Prevents corrosion

Question 7

What in the electrolyte conduct electricity

Answer 7

Free ions

Question 8

What is an electrolyte

Answer 8

It is an ionic substance

Question 9

What half equations happen at the cathode and the anode of molten sodium chloride . Cl- and Na+

Answer 9

Cathode - Na+ + e- to Na

Anode - 2Cl - to Cl2 plus 2 e-

Question 10

Which ions are attracted to which electrodes

Answer 10

The anion is attracted to the anode because the anion is negative the anode is positive. The cation is attracted to the cathode as the cation is positive and is attracted to the negative cathode

Question 11

What is oxidation and where does it occur

Answer 11

It is the loss of electrons so occurs at the anode where negative ions loose electrons

Question 12

What is reduction and where does it happen

Answer 12

It is gaining of electrons so occurs at the cathode because the cations are positive they need electrons . Na+ + E- to Na

Question 13

What are the half equations for molten lead bromide Pb2+

Br-

Answer 13

Cathode Pb2+ + 2e- to Pb

Anode 2Br- to Br2 plus 2e-, there are two bromide reactants as it forms a diatomic molecule

Question 14

Why is electrolysis of solutions different to molten substances

Answer 14

Molten ionic salts only contain the ions of that salt. But solutions also have H+ and OH- ions from the water

Question 15

In electrolysis of solutions which ion is discharged at the anode

Answer 15

The simplest one, for example Cl is discharged instead of OH and OH is discharged instead of SO4

Question 16

What happens at the cathode in electrolysis of solutions

Answer 16

The metal will be discharged if it’s less reactive than hydrogen . For example copper is less reactive than hydrogen so is discharged in electrolysis of copper salts. But sodium is more reactive than hydrogen so hydrogen will be discarded for sodium salts and the sodium will collect at the bottom

Question 17

What’s the half equation for hydroxide discharging at the anode

Answer 17

40H- to 2H20 + 02 + 4e-

Question 18

How can you purify copper

Answer 18

By electrolysis

Question 19

Where does impure copper start in electrolysis

Answer 19

The anode it

Question 20

What is used for the cathode in copper purification

Answer 20

Pure copper

Question 21

Describe how copper if purified

Answer 21

Electrons are pulled of the atoms at the anode they go into solution as Cu2+ ions. At the cathode they gain electrons and become Cu . Impurities at the anode are dropped as sludge.

Question 22

What happens at the anode in copper sulfate purifation

Answer 22

Copper atoms dissolve form the impure anode

Cu -> Cu2+ + 2e-

Question 23

How can you show that copper atoms are moving from anode to cathode

Answer 23

Weigh the anode and cathode before the electrolysis and weigh them after

Question 24

What is electroplating

Answer 24

The process of coating a metal with another metal using electricity

Question 25

Which electrode is the object you want to plate

Answer 25

Usually the cathode

Question 26

Why electroplate

Answer 26

For jewellery improves the appearance making them shinty and attractive. To prevent corrosion. Some cutlery is electroplated as it is iron and the stops it oxidising with oxygen