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Hertswood Academy Chemistry GCSE > C6- Electrolysis > Flashcards

C6- Electrolysis Flashcards

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1
Q
  1. What happens to the ions when an ionic compound is melted or dissolved in water?
A

The ions become free to move about within the liquid or solution.

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2
Q
  1. What do we call liquids or solutions of melted or dissolved ionic compounds?
A

Electrolytes

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3
Q
  1. Do electrolytes conduct electricity?
A

Yes

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4
Q
  1. What happens to the ions when an electric current is passed through an electrolyte?
A

The current causes the ions to move to the electrodes.

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5
Q
  1. Where do positively charged ions move to?
A

Positively charged ions move to the negative electrode (the cathode)

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6
Q
  1. Where do negatively charged ions move to?
A

Negatively charged ions move to the positive electrode (the anode).

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7
Q
  1. What is electrolysis?
A

Positively charged ions move to the negative electrode (the cathode), and negatively charged ions move to the positive electrode (the anode). Ions are discharged at the electrodes producing elements

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8
Q
  1. What happens when a simple ionic compound is electrolysed in the molten state using inert electrodes?
A

Metal is produced at the cathode and the non-metal) is produced at the anode.

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9
Q
  1. What happens when lead bromide is electrolysed in the molten state using inert electrodes?
A

Lead is produced at the cathode and bromine is produced at the anode.

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10
Q
  1. What do the ions discharged when an aqueous solution is electrolysed depend on?
A

They depend on the relative reactivity of the elements involved.

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11
Q
  1. What happens at the negative electrode (cathode), if the metal is more reactive than hydrogen?
A

Hydrogen is produced

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12
Q
  1. What happens at the positive electrode (anode) if there are no halide ions present?
A

Oxygen is produced

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13
Q
  1. What happens at the positive electrode (anode) if the solution contains halide ions?
A

The halogen is produced.

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14
Q
  1. At the negative electrode (cathode), hydrogen is produced if the metal is more reactive than hydrogen. At the positive electrode (anode), oxygen is produced unless the solution contains halide ions when the halogen is produced. Why does this happen?
A

This happens because in the aqueous solution water molecules break down producing hydrogen ions and hydroxide ions that are discharged.

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15
Q
  1. How can metals be extracted from molten compounds?
A

Metals can be extracted from molten compounds using electrolysis.

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16
Q
  1. How else can metals be extracted?
A

Metals can be extracted by reduction with carbon

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17
Q
  1. When is electrolysis used?
A

Electrolysis is used if the metal is too reactive to be extracted by reduction with carbon or if the metal reacts with carbon.

18
Q
  1. How much energy is used in electrolysis?
A

Large amounts of energy are used during electrolysis

19
Q
  1. What is the energy used for during electrolysis?
A

Large amounts of energy are used in the extraction process to melt the compounds and to produce the electrical current.

20
Q
  1. How is aluminium metal manufactured from aluminium oxide by electrolysis?
A

Aluminium is manufactured by the electrolysis of a molten mixture of aluminium oxide and cryolite using carbon as the positive electrode (anode).

21
Q
  1. Why is a mixture of aluminium oxide and cryolite used as the electrolyte?
A

To reduce the melting point of the aluminium oxide, so that less energy is needed to melt it.

22
Q
  1. Why must the positive electrode (anode) be continually replaced?
A

The positive electrode (anode) which is made of carbon reacts with two oxygen ions,
producing carbon dioxide gas. This means that the positive electrode slowly gets smaller.

23
Q
  1. Describe what happens at the cathode (negative electrode) during electrolysis and state the name of that type of reaction
A

At the cathode (negative electrode), positively charged ions gain electrons. These are reduction reactions.

24
Q
  1. Describe what happens at the anode (positive electrode) during electrolysis and state the name of that type of reaction
A

At the anode (positive electrode), negatively charged ions lose electrons. These are oxidation reactions.

25
Q
  1. How can the reactions at electrodes be represented?
A

Reactions at electrodes can be represented by half equations, for example:
2H+ + 2e− → H2 and 4OH− → O2 + 2H2O + 4e− or 4OH− − 4e− → O2 + 2H2O

26
Q
  1. What do the ions discharged when an aqueous solution is electrolysed depend on?
A

They depend on the relative reactivity of the elements involved.

27
Q
  1. What happens at the negative electrode (cathode), if the metal is more reactive than hydrogen?
A

Hydrogen is produced

28
Q
  1. What happens at the positive electrode (anode) if there are no halide ions present?
A

Oxygen is produced

29
Q
  1. What happens at the positive electrode (anode) if the solution contains halide ions?
A

The halogen is produced.

30
Q
  1. At the negative electrode (cathode), hydrogen is produced if the metal is more reactive than hydrogen. At the positive electrode (anode), oxygen is produced unless the solution contains halide ions when the halogen is produced. Why does this happen?
A

This happens because in the aqueous solution water molecules break down producing hydrogen ions and hydroxide ions that are discharged.

31
Q
  1. How can metals be extracted from molten compounds?
A

Metals can be extracted from molten compounds using electrolysis.

32
Q
  1. How else can metals be extracted?
A

Metals can be extracted by reduction with carbon

33
Q
  1. When is electrolysis used?
A

Electrolysis is used if the metal is too reactive to be extracted by reduction with carbon or if the metal reacts with carbon.

34
Q
  1. How much energy is used in electrolysis?
A

Large amounts of energy are used during electrolysis

35
Q
  1. What is the energy used for during electrolysis?
A

Large amounts of energy are used in the extraction process to melt the compounds and to produce the electrical current.

36
Q
  1. How is aluminium metal manufactured from aluminium oxide by electrolysis?
A

Aluminium is manufactured by the electrolysis of a molten mixture of aluminium oxide and cryolite using carbon as the positive electrode (anode).

37
Q
  1. Why is a mixture of aluminium oxide and cryolite used as the electrolyte?
A

To reduce the melting point of the aluminium oxide, so that less energy is needed to melt it.

38
Q
  1. Why must the positive electrode (anode) be continually replaced?
A

The positive electrode (anode) which is made of carbon reacts with two oxygen ions, producing carbon dioxide gas. This means that the positive electrode slowly gets smaller.

39
Q
  1. Describe what happens at the cathode (negative electrode) during electrolysis and state the name of that type of reaction
A

At the cathode (negative electrode), positively charged ions gain electrons. These are reduction reactions.

40
Q
  1. Describe what happens at the anode (positive electrode) during electrolysis and state the name of that type of reaction
A

At the anode (positive electrode), negatively charged ions lose electrons. These are oxidation reactions.

41
Q
  1. How can the reactions at electrodes be represented?
A

Reactions at electrodes can be represented by half equations, for example:
2H+ + 2e− → H2 and 4OH− → O2 + 2H2O + 4e− or 4OH− − 4e− → O2 + 2H2O

Hertswood Academy Chemistry GCSE (9 decks)

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