Electrolysis

Question 1

How is an ammeter calibrated using electrolysis?

Answer 1

A copper voltameter is set up with the ammeter to be calibrated in the circuit. The copper cathode is weighed

Question 2

State Faraday’s first law of electrolysis.

Answer 2

The mass

Question 3

State Faraday’s second law of electrolysis.

Answer 3

The masses of different substances deposited or liberated by the same quantity of electricity are directly proportional to the chemical equivalents of the substances.

Question 4

What is the mathematical expression of Faraday’s first law?

Answer 4

M ∝ Q or M ∝ It

Question 5

What is the electrochemical equivalent (e.c.e.) of a substance?

Answer 5

The constant of proportionality (Z) in the equation M = ZIt. It is the mass of that substance deposited by one Coulomb of electricity (or by 1 amp in 1 sec.) in a process of electrolysis. Its unit is g/Coulomb.

Question 6

Describe the experimental verification of Faraday’s first law of electrolysis.

Answer 6

A copper voltameter is set up

Question 7

A

Question 8

What is observed in the electrolysis of acidulated water?

Answer 8

Oxygen forms in the tube above the Anode and hydrogen above the Cathode. The ratio of the volume of oxygen to the hydrogen formed is 1:2.

Question 9

What ions does water dissociate into during electrolysis?

Answer 9

Hydrogen ions (H⁺) and hydroxyl ions (OH⁻).

Question 10

What ions does sulphuric acid dissociate into?

Answer 10

Hydrogen ions and sulphate ions (SO₄²⁻).

Question 11

What happens to H⁺ ions during electrolysis of acidulated water?

Answer 11

They drift to the cathode and are discharged there

Question 12

What happens to OH⁻ ions during electrolysis of acidulated water?

Answer 12

They drift to the anode and are discharged

Question 13

What is observed in the electrolysis of copper sulphate solution with copper electrodes?

Answer 13

A fresh bright coating of copper forms over the cathode

Question 14

What ions does copper sulphate in solution dissociate into?

Answer 14

Copper ions (Cu²⁺) and sulphate ions (SO₄²⁻).

Question 15

What ions does water break down into?

Answer 15

Hydrogen ions (H⁺) and hydroxyl ions (OH⁻).

Question 16

What happens to copper and hydrogen ions during electrolysis of copper sulphate solution?

Answer 16

They drift to the cathode

Question 17

What happens to sulphate and hydroxyl ions during electrolysis of copper sulphate solution?

Answer 17

They drift to the anode

Question 18

What is the overall result of electrolysis of copper sulphate solution with copper electrodes?

Answer 18

Copper flows from the anode to the cathode

Question 19

What is observed in the electrolysis of copper sulphate solution using platinum electrodes?

Answer 19

The platinum cathode is covered with a bright-red layer of pure copper. The copper sulphate solution loses its blue color.

Question 20

What happens to copper and hydrogen ions during electrolysis of copper sulphate solution with platinum electrodes?

Answer 20

They drift to the cathode where copper is discharged in preference to hydrogen.

Question 21

What happens to hydroxyl ions at the anode during electrolysis of copper sulphate solution with platinum electrodes?

Answer 21

They are discharged and combine to give water and oxygen.

Question 22

What is the net result of electrolysis of copper sulphate solution with platinum electrodes?

Answer 22

Copper is deposited on the cathode

Question 23

What are some applications of electrolysis?

Answer 23

Electroplating of metals

Question 24

What is electroplating?

Answer 24

The process of coating a metallic object with another metal to improve its appearance or protect it against corrosion.

Question 25

What metals can be used to electroplate other metallic objects?

Answer 25

Copper

Question 26

Give examples of objects that are often electroplated.

Answer 26

Bumpers of cars and handlebars of bicycles (chromium-plated)

Question 27

What is used as the cathode in electroplating?

Answer 27

The material to be electroplated.

Question 28

What is used as the anode in electroplating?

Answer 28

The electroplating material.

Question 29

What is the electrolyte used in electroplating?

Answer 29

A solution of the salt of the metal to be deposited.

Question 30

Describe the silver-plating of spoons.

Answer 30

Spoons are made the cathode of a voltameter containing a silver nitrate solution

Question 31

What is electrolysis?

Answer 31

The chemical change in a liquid due to the flow of electric current through the liquid.

Question 32

Who extensively studied electrolysis?

Answer 32

Michael Faraday.

Question 33

What are good conductors of electricity known as?

Answer 33

Electrolytes.

Question 34

What are poor conductors of electricity known as?

Answer 34

Non-electrolytes.

Question 35

Give examples of liquids that are generally good conductors.

Answer 35

Solutions of acids

Question 36

Give examples of liquids that are poor conductors.

Answer 36

Benzene and paraffin or kerosene.

Question 37

What type of compounds are generally poor conductors?

Answer 37

Organic compounds.

Question 38

Is pure water a good or poor conductor?

Answer 38

Poor conductor.

Question 39

What happens to water containing some dissolved salts?

Answer 39

Conducts moderately.

Question 40

What is a Voltameter?

Answer 40

A device for studying the flow of current through a liquid.

Question 41

What are the main parts of a Voltameter?

Answer 41

The Electrolyte and Electrodes.

Question 42

What is the Electrolyte?

Answer 42

The liquid or molten substance which conducts a current and is decomposed by it.

Question 43

What are Electrodes?

Answer 43

Materials in the form of a rod or plate through which current enters or leaves the electrolyte.

Question 44

What is the positive electrode called?

Answer 44

Anode.

Question 45

What is the negative electrode called?

Answer 45

Cathode.

Question 46

What are ions?

Answer 46

Positively and negatively charged particles in an electrolyte.

Question 47

What is electrolytic dissociation?

Answer 47

The process by which molecules of the electrolyte are split in solution into ions.

Question 48

Does electrolytic dissociation require an electric field?

Answer 48

No

Question 49

What is the movement of ions in an electrolyte before a battery is connected?

Answer 49

Random movements.

Question 50

What happens to ions when a p.d. is set up across the electrodes?

Answer 50

Positive ions drift to the cathode (negative potential) and negative ions drift to the anode (positive potential).

Question 51

What constitutes the electric current flowing through the electrolyte?

Answer 51

The directional movement of ions.

Question 52

What happens to ion movement when the battery is disconnected?

Answer 52

The directional movement ceases

Question 53

Why can electrolytic solutions conduct electricity?

Answer 53

Because the electrolytes in solution can dissociate into ions.

Question 54

Why don't non-electrolytes in solution easily conduct electricity?

Answer 54

Because they do not easily dissociate into ions.