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Chemistry IGCSE > Electrolysis > Flashcards

Electrolysis Flashcards

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1
Q

Define ‘Electrolysis’

A

Electrolysis is the breakdown of an ionic compound in an aqueous solution by the passage of electricity.

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2
Q

Describe the electrolysis molten lead(II) bromide.

A

At the cathode: Lead is produced.

At the Anode: Bromine gas is produced. It is a brown gas.

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3
Q

Describe the transfer of ions and electrons in an electrolytic shell from the electrolyte to the electrodes.

A

Negative ions move to the anode and lose their electrons.
These electrons travel from the anode to the cathode through the conducting metal wire of the external circuit.
At the cathode, the positive ions gain electrons.

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4
Q

What is an ore?

A

An ore is a rock containing a metal or metal compound in high enough proportion, that it is economical to be extracted.

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5
Q

What are the products of the electrolysis of aluminium.

A

Anode: Oxygen gas
Cathode: Aluminium.

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6
Q

What is the ore for Aluminium?

A

Bauxite

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7
Q

Why is cryolite used in the electrolysis of Aluminium?

A
  • To reduce the melting point of it so that it is economical to breakdown.
  • To act as a solvent for the Aluminium ions.
  • To improve the electrical conductivity.
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8
Q

why do the carbon anodes have to be replaced frequently, in aluminium electrolysis?

A

The oxygen formed at the anode reacts with the graphite(carbon) anode to form carbon dioxide gas. Therefore the anodes burn away, and have to e replaced frequently.

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9
Q

Identify 3 uses for aluminium. Explain how its’s properties allow for that purpose.

A
  • Manufacture of air crafts. Aluminium has a low density and is therefore lightweight for its size. It is also strong and can be made stronger by alloys.
  • Used in food containers. It forms a layer of aluminium oxide that is resistant to corrosion.
  • Used in overhead electric cables. It is a good conductor. It also has a low density, meaning it won’t stretch and break under its own weight.
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10
Q

Explain why aluminium has a high melting point.

A

there are very strong attractive forces between Al3+ and O2- ions. This requires a great deal of energy to break.

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11
Q

Name the type of particle responsible for the transfer of charge in wires and the electrolyte.

A

Wires- Electrons.

Electrolyte- ions.

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12
Q

Explain why aluminium takes time to react with (dilute hydrochloric) acid.

A

Aluminium has a coating of aluminium oxide.

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13
Q

Describe the electrolysis of concentrated hydrochloric acid.

A

Anode: Chlorine gas
Cathode: Hydrogen gas.
It is Cl gas as it is more concentrated.

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14
Q

Describe the electrolysis of concentrated sodium chloride.

A

-Anode: Hydrogen gas.
Hydrogen is discharged as Na is more reactive than Hydrogen.
-Cathode: Chlorine gas.
Because it is more concentrated than OH-

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15
Q

Describe the electrolysis of dilute aqueous sodium chloride.

A

-Anode: Oxygen gas and water. Along with 4 electrons.
OH is discharged as it more concentrated than Cl-
-Cathode:Hydrogen gas is released.
Sodium ions stay in the solution as they are more reactive than hydrogen ions.

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16
Q

How is chlorine, hydrogen and sodium hydroxide manufactured using electrolysis. [6]

A
  • The solution contains Na+,Cl-,OH- and H+ ions.
  • Hydrogen is produced at the cathode.
  • Chlorine is produced at the anode.
  • This means, H+ and Cl- ions are removed from the solution.
  • The Na+ and OH- ions react to form NaOH.
  • The NaOH is concentrated by heating to evaporate some of the water.
17
Q

Describe the electrolysis of dilute sulfuric acid.

A

-Anode: Oxygen gas is produced.
-Cathode: Hydrogen gas is produced.
Sulfate ions always stay in the solution.

18
Q

Describe the electrolysis of aqueous copper(II) sulfate, using copper electrodes and carbon electrodes.

A
  • Carbon(graphite) electrodes:
  • Anode: Oxygen and water.
  • Cathode: Copper.
  • Copper electrodes:
  • Anode: Copper reduced.
  • Cathode: Copper oxidized.
19
Q

How is copper purified using electrolysis.

A

Impure copper is used for the anode and pure copper is used for the cathode. The copper(II) ions from the impure anode will transfer to the copper cathode and the pure copper cathode will increase in mass.

Most impurities fall to the bottom. However, some like Zn2+ go into the solution. They do not discharge at the cathode because they are very dilute.

20
Q

Describe the two main uses of copper, and the properties that make them useful for that use.

A
  • Used in electrical wiring as it is a good conductor.

- Used in cooking utensils as it has a high melting point, does not react with water and is a good conductor.

21
Q

Define electroplating.

A

is the process of applying a thin layer of a metal to another metal using electrolysis.

22
Q

At which electrode is the object to be electroplated kept?

A

Cathode.

23
Q

How id the electrolyte chosen for electroplating.

A

it is a solution of a salt of the same metal that is being used for the anode.

24
Q

Describe the use of electroplating.

A

-preventing corrosion. used in food can and containers. they are coated with a thin layer of thin. It prevents air from coming to contact with the steel, so it does not corrode.

25
Q

Why should object being electroplated be fee from any dirt or grease.

A
  • coating will not stick
  • in order to have an even coating
  • Dirt or grease will be trapped.
26
Q

Suggest suitable materials for the electrodes used in electroplating.

A
  • Platinum

- Carbon(graphite)

27
Q

when is there a flow of a electric current in a simple electrolysis cell.

A

When two metals of different reactivity is dipped into the electrolyte, they produce electrical energy and an electric current flows thorough the wire connecting them.

28
Q

Describe that electron flow in a cell with zinc and copper electrodes.

A
  • Zinc losses its electrons, so it is oxidized; Zn - > Zn2+ +2e-
  • These electrons travel through the wire to the copper electrode.
  • The zinc ions go into the solution.
  • Zinc is the negative pole of the cell.
  • Copper gains electrons, so it is reduced: Cu2+ +2e- - >Cu .
  • Copper is the positive pole of the cell.
29
Q

In an electrolysis cell, when is the voltage released the highest.

A

When there is a greatest difference in the reactivity

Chemistry IGCSE (10 decks)

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