Electrolysis

Question 1

What is electrolysis?

Answer 1

Electrolysis is a process in which an electric current passes through an electrolyte that conducts electricity leading to the decomposition of the electrolyte.

Question 2

What is the electrode of a typical electrolytic cell?

Answer 2

Electrodes are the electrical contacts that complete the electric circuit between the conducting wire and the electrolyte. The two electrodes are called cathode and anode.

Question 3

What are the features of the cathode of a typical electrolytic cell?

Answer 3

The cathode allows electrons to enter the electrolyte. The ions in the electrolyte are reduced here.
It is connected to the negative terminal of a power source.

Question 4

What is the anode of a typical electrolytic cell?

Answer 4

The anode allows electrons to leave the electrolyte. The ions in the electrolyte are oxidised here.
It is connected to the negative terminal of a power source.

Question 5

What are electrolytes?

Answer 5

Electrolytes are substances that contain mobile ions when in molten or aqueous form.

Question 6

What is the direction of movement of ions in the electrolyte during electrolysis?

Answer 6

Positive ions move towards the cathode and negative ions move towards the anode.

Question 7

Why are positive ions attracted to the cathode?

Answer 7

Electrons from the negative terminal of the power source enter the electrolyte through the cathode. The positive ions gain the electrons.

Question 8

Why are negative ions attracted to the anode?

Answer 8

Electrons donated by the negative ions leave the electrolyte and flow back to the positive terminal of the power source to complete the circuit.

Question 9

How is electricity conducted in an electrolytic cell?

Answer 9

By free electrons in the conducting wire, or by mobile positive ions and negative ions in the electrolyte.

Question 10

What is the reaction taking place at the cathode?

Answer 10

Positive ions gain electrons to become an element.
Half equation: Aˣ⁺ + xe⁻ → A
Reduction occurs.

Question 11

What is the reaction taking place at the anode?

Answer 11

Negative ions lose electrons to become an element.
Half equation: Bˣ⁻ → B + xe⁻
Oxidation occurs.

Question 12

What are inert electrodes?

Answer 12

Inert electrodes are unreactive electrodes that do not take part in the chemical reaction during electrolysis. Selective discharge of ions will occur.

Question 13

What are some examples of inert electrodes?

Answer 13

Carbon/graphite, platinum

Question 14

What is selective discharge?

Answer 14

At any one time, only one type of ion can be discharged at the respective electrodes.

Question 15

What affects the selective discharge of cations?

Answer 15

Reactivity series.

The less reactive cation is selectively discharged first.

Question 16

What affects the selective discharge of anions?

Answer 16

Concentration effect. In a dilute solution, hydroxide ions are selectively discharged. In a concentrated solution, the more concentrated anions are selectively discharged.

Question 17

What is electroplating?

Answer 17

Electroplating is a process for coating an object with a layer of a desired metal.

Question 18

Which object is placed at the anode in a typical electrolytic setup of electroplating?

Answer 18

The desired metal to coat an object.

Question 19

Which object is placed at the cathode in a typical electrolytic setup of electroplating?

Answer 19

The object to be coated. When the cations of the desired metal are discharged, the product deposits on the surface of the object.

Question 20

What are the typical observations at the respective electrodes in electroplating
?

Answer 20

The desired metal shrinks in size and a layer of metal is deposited on the object.

Question 21

Which object is placed at the anode in a typical electrolytic setup for purifying a metal?

Answer 21

The impure sample containing the desired metal.

Question 22

Which object is placed at the cathode in a typical electrolytic setup for purifying a metal?

Answer 22

The pure desired metal plate.

Question 23

What are the typical observations at the respective electrodes when purifying a metal??

Answer 23

The impure sample shrinks in size. Impurities sink at the bottom of the beaker. The pure metal plate gains mass or increases in size.

Question 24

What is a simple cell?

Answer 24

A simple cell is a device which converts chemical energy to electrical energy.

Question 25

How is electrical energy generated in the simple cell?

Answer 25

Oxidation and reduction takes place together at the anode and cathode respectively to cause the electrons to flow in a simple cell. Thus, redox is responsible for generating electrical energy in the simple cell.

Question 26

What is the suitable electrolyte in a simple cell?

Answer 26

Any solution with mobile ions, e.g. acid, alkali or salt solution

Question 27

What is the main feature of the electrodes used in a simple cell?

Answer 27

Two metals of different reactivity

Question 28

Which metal acts as the anode in a simple cell and why?

Answer 28

The more reactive metal, as it is where atoms of the more reactive metal loses electrons. Oxidation occurs here.