C6-Electrolysis

Question 1

Electrolysis

Answer 1

Using electricity to split up substances (decomposition of ionic compounds using electricity)

Question 2

Cathode(-)

Answer 2

To the right and attracts ca(+)ions as they are opposite charge

Question 3

Anode(+)

Answer 3

To the left attracts anions(-)as opposite cahrge

Question 4

Addition of oxygen

Answer 4

Oxidation

Question 5

Removal of oxygen

Answer 5

Reduction

Question 6

Addition of hydrogen

Answer 6

Reduction

Question 7

Removal of hydrogen

Answer 7

Oxidation

Question 8

Discharge rule at the cathode

Answer 8

Least reactive gets discharged

Question 9

Brine

Answer 9

Concentrated sodium chloride solution that can undergo electrolysis to produce chlorine gas, hydrogen gas and sodium hydroxide solution

Question 10

Electrolyte

Answer 10

A liquid, containing free-moving ions, which is broken down by electricity in the process of electrolysis

Question 11

Half equation

Answer 11

An equation that describes reduction (gain of electrons) or oxidation (loss of electrons)

Question 12

Inert

Answer 12

Unreactive

Question 13

Molten ionic compounds

Answer 13

The metal and non-metal ions within the molten ionic compound become free to move, so the liquid can undergo electrolysis

Question 14

Metal ions

Answer 14

Since metal ions are positive (cations) they will be attracted to the negative electrode (cathode)where the metal will form

Question 15

Non-metal ions

Answer 15

Since non-metal ions are negative(anions), they will be attracted to the positive electrode (anode), where the non-metal will form

Question 16

Electrolysis is used to extract reactive metals from molten ores (melted materials containing metals). It is used to extract metals such as aluminium which

Answer 16

Are more reactive than carbon

Question 17

What is formed at the anode(positive electrode)for the extraction of alluminium

Answer 17

Carbon dioxide is formed, the anode is usually made up of carbon because it is a good conductor and it is cheap

Question 18

What is formed at the cathode (negative electrode)for the extraction of aluminium

Answer 18

The aluminium is formed at the cathode

Question 19

Disadvantages of electrolysis to extract alluminium

Answer 19

Lots of energy is needed to melt the solid ionic compound to allow the ions to flow and to produce the electrical current. Also all this energy costs money, and a lot of it!

Question 20

Electrolysis of aqueous solutions the products are difficult to predict because

Answer 20

The water molecules in the solution split up to form hydrogen (H+)and hydroxide (OH-)ions

Question 21

What forms at the anode(positive electrode) for aqueous solutions

Answer 21

If halide ions are present, the respective halogen forms and if they are absent oxygen forms

Question 22

What forms at the cathode (negative electrode) for aqueous solutions

Answer 22

If the metal’s more reactive than hydrogen, hydrogen is produced but if the metal’s less reactive than hydrogen, the metal is produced

Question 23

Half equatiosm

Answer 23

Show the reactions that happen at each electrode

Question 24

Half equation at the cathode(negative electrode)

Answer 24

Reduction reaction happens (positively charged ions gain electrons)e.g.Pb2+ +2e- ->Pb

Question 25

Half equation at the anode(positive electrode)

Answer 25

Oxidation reactions happen (negatively charged ions lose electrons)e.g.2Br- ->Br2 +2e-

Question 26

The electrolytes are made up of

Answer 26

of an unreative or inert substance such as graphite so it doesn’t react with electrolyte or the products made in electrolysis.

Question 27

At the electrodes they

Answer 27

lose their charge and become elements but this depends on the compound used and whether it is molten or dissolved in water.

Question 28

Most ionic compounds have

Answer 28

very high melting points so a lot of energy is needed in order to melt and free their ions.

Question 29

Some ionic compounds can

Answer 29

dissolve in water which also frees the ions.

Question 30

It is difficult to predict what will be formed when electrolysing ionic compounds in solution because

Answer 30

the water also forms ions, so the products may be different.

Question 31

Covalent compounds can’t usually be electrolysed unless

Answer 31

They react in water

Question 32

Why must the ionic compound be

molten or dissolved?

Answer 32

Because the forces of attraction are broken and the ions are free to move so they can conduct electricity