Electrolisis

Question 1

What is electrolysis?

Answer 1

Electrolysis is the chemical process of using an electrical current to stimulate non-spontaneous reactions.
The decomposition of a chemical substance (in solution or the molten state) by the application of electrical energy.

Question 2

What is a non spontaneous reaction?

Answer 2

A reaction that needs energy to work while it proceeds.

The process would not happen on its own, as it goes in an unfavorable, or a reversed, direction.

Question 3

What is an electrolytic cell?

Answer 3

An electric cell in which a non-spontaneous redox reaction is made to occur by the application of an external potential difference across the electrodes.

Question 4

What is the process of electrolysis?

Answer 4

Passage of an electric current through an electrolytic solution causes the chemical reaction called electrolysis.

Question 5

What are the features of an electrolytic cell?

Answer 5

• electrolyte solution
• two electrodes
• an external source of energy

Question 6

Are the products of electrolysis for molten and ionic compounds predictable?

Answer 6

The products of the electrolysis of molten ionic compounds are predictable whereas the products of the electrolysis of an aqueous solution may be affected by factors including concentration, the nature of the electrolyte and the nature of the electrodes.

Question 7

Energy transformations of an electrolytic cell?

Answer 7

.

Question 8

What is the function of electrolysis?

Answer 8

Electrolysis can be used to produce highly reactive elements such as the strong reducing agent metals in groups 1 and 2 in the periodic table as well as chlorine and fluorine, since production by chemical reduction is not practical.

Question 9

What is a rechargeable cell?

Answer 9

A secondary cell that can be recharged after it becomes ‘flat’.

Question 10

How is a secondary cell both galvanic and electrolytic?

Answer 10

The cell uses spontaneous redox reactions to produce electricity during discharge, but they become electrolytic when converting electrical energy back into chemical energy when they are recharged.

Question 11

What is the discharge process?

Answer 11

When a secondary cell produces energy, essentially becoming galvanic.

Question 12

What is the recharge process?

Answer 12

When a secondary cell requires an input of energy, essentially becoming electrolytic. Forcing electrons to travel in the reverse direction and, because the discharge products are still in contact with the electrodes, the original reactions are reversed.

Question 13

What polarity are the electrodes in electrolysis?

Answer 13

anode: positive
cathode: negative

Question 14

What is electroplating?

Answer 14

Process of coating an object with a thin film of metal deposited from an electrolytic solution by electrolysis.

Question 15

Which electrode is the object that is being electroplated ket in contact with?

Answer 15

The cathode, as the cathode gains electrons which combine with the ions in the electrolytes, forming solids.

Question 16

What factor do you have to take into consideration during the electrolysis of aqueous solutions?

Answer 16

When aqueous solutions are electrolysed, water may react at one or both electrodes.

Question 17

What factors effect the electrolysis of aqueous solutions?

Answer 17

• the concentration of the electrolyte
• the nature of the electrolyte
• the nature of the electrodes.

Question 18

What are the factors effecting electroplating?

Answer 18

In the plating solution, the concentration of the cations to be reduced is carefully controlled. Unwanted side reactions must be avoided.
The type and concentration of electrolyte needs careful consideration.
The solution must contain compounds to control the acidity and increase the conductivity.
Some compounds make the metal coating brighter or smoother.
In many electroplating cells, the anode must be shaped like the object at the cathode to achieve an even metal coating.

Question 19

What is Faradays first law of electrolysis?

Answer 19

The amount of current passed through an electrode is directly proportional to the amount of material released from it.

Question 20

What is Faradays second law of electrolysis?

Answer 20

In order to produce 1mole of a substance by electrolysis, 1, 2, 3 or another whole number of moles of electrons (faradays) must be consumed, according to the relevant half-cell equation.

Question 21

Explain faradays second law of electrolysis?

Answer 21

1 mole of electrons is required to discharge 1 mole of an ion.
Ag+(aq) + e- → Ag(s)
Therefore 1 faraday (96500 C) is needed to 1 mole of atoms.

Question 22

Equation to find the number of electrons?

Answer 22

n(e-) = Q ÷ F

Question 23

Equation to find the electric charge?

Answer 23

Q = I x t

Question 24

What is a faraday?

Answer 24

Charge carried by 1 mole of electrons?

= 96500 C

Question 25

State the name of each symbol:
Q
I
t
C
F
A

Answer 25

Q: electric charge in coulombs  
I: current in amperes 
t: time in seconds
C: coulomb- unit of electric charge 
F: faraday- 96500 C
A: amperes- unit for current

Question 26

How is battery life affected?

Answer 26

Can be affected by temperature, depth of discharge and operating voltage.
These can reduce its ability to be fully recharged and affect its safe operation.

Question 27

In an electrolytic cell, electrodes are the…?

Answer 27

electrical conductors

Question 28

In a secondary cell…?

Answer 28

The positively charged cathode in the discharging reaction becomes the positively charged anode in the recharging process

Question 29

What is important about the products in a rechargeable cell

Answer 29

They must remain in contact with the electrodes.

Question 30

Why is it referred to as the ‘minimum’ voltage required for reaction to occur?

Answer 30

The minimum EMF is to allow reaction to reach neutrality, plus a suitable over potential to overcome friction/ resistance in wire.

Question 31

What are the signs that electrolysis are taking place?

Answer 31

• change in PH, producing OH-or H+
• gas produced at electrodes
• solids produced at electrodes

Question 32

Why is there a narrow range in voltage that can be supplied to electrolytic cell?

Answer 32

The voltage can’t be too high as unwanted side reactions could occur.