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AS Chemistry > ES - Electrolysis > Flashcards

ES - Electrolysis Flashcards

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1
Q

What is electrolysis?

A

Breaking a substance down using electricity.

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2
Q

What does electrolysis require?

A

A liquid to conduct the electricity - electrolyte.

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3
Q

What are electrolytes?

A

Liquids that conduct electricity.

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4
Q

Why do electrolytes conduct electricity?

A

They contain free ions - molten or dissolved ionic substance.

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5
Q

What are negative ions called?

A

Anions.

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6
Q

What are positive ions called?

A

Cations.

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7
Q

What is the positive electrode called?

A

Anode.

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8
Q

What is the negative electrode called?

A

Cathode.

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9
Q

Where are anions attracted to in electrolysis?

A

Anode.

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10
Q

Where are cations attracted to in electrolysis?

A

Cathode.

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11
Q

What happens to anions at the anode?

A

They lose electrons.

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12
Q

What happens to cations at the cathode?

A

They gain electrons.

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13
Q

Describe the procedure for electrolysis of an aqueous solution:

A

Use wires and clips to connect each electrode to the power supply. The electrode connected to the positive pole will be the anode and the electrode that is connected to the negative pole will be the cathode.

You usually use inert electrodes (such as platinum or carbon) so they don’t start reacting and interfering with the electrolysis.

Place the electrodes into a beaker containing the electrolyte making sure that the electrodes aren’t touching each other.

Turn the power supply on.

Depending on the electrolyte, the products will form as metals (as a thin layer on the surface of the cathode - known as plating) or as gases (as bubbles at the cathode or anode).

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14
Q

How can you show what happens at each electrode in electrolysis?

A

Using half equations.

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15
Q

In molten ionic compounds, how many sources of ions are there?

A

1

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16
Q

What do half equations show?

A

The movement of electrons during a reaction.

17
Q

What will the half equation for the cathode show?

A

Positive ions gaining electrons to form atoms.

18
Q

What will the half equation for the anode show?

A

Negative ions losing electrons to form atoms.

19
Q

In the electrolysis of aqueous solutions, the products formed at each electrode depends on what?

A

The reactivity of the ions as well as the concentration of the salt solution.

20
Q

What will happen at the cathode if the metal is less reactive than hydrogen (e.g. copper or silver)?

A

Then the metal will be formed.

21
Q

What will happen at the cathode if the metal is more reactive than hydrogen (e.g. all of group 1 and group 2 metals and aluminium)?

A

Hydrogen gas will be formed from hydrogen ions in the water.

22
Q

What will happen at the anode if the solution doesn’t contain a halide?

A

Oxygen will be formed from hydroxide ions in the water.

23
Q

What will happen at the anode if the solution is concentrated and contains a halide?

A

The halogen will be formed.

24
Q

What will happen at the anode if the solution contains a halide but is dilute?

A

Oxygen will be formed from hydroxide ions in the water.

25
Q

If you use metal electrodes (apart from platinum), what can also be made at the anode?

A

Metal ions.

26
Q

In the purification of copper, what electrodes are used?

A

The anode is made from impure copper and the cathode is made from pure copper.

27
Q

What happens at the electrodes in the purification of copper?

A

At the anode, copper atoms lose electrons and become copper ions which enter the solution. These ions are then attracted to the cathode where they gain electrons to become copper atoms again and plate the pure copper cathode.

The pure cathode increases in mass, the impure anode shrinks.

28
Q

What is plating?

A

When metal products form as a thin layer on the surface of the cathode in electrolysis of an aqueous solution.

29
Q

What is formed at the cathode if the metal in the salt isn’t from group 1 or 2 or isn’t aluminium?

A

The metal.

30
Q

What is formed at the cathode in the electrolysis of acids?

A

Hydrogen.

31
Q

What is formed at the anode if the salt is a halide?

A

The halogen.

32
Q

What is formed at the anode if the salt is a nitrate or sulfate?

A

Oxygen.

33
Q

What is formed at the anode in the electrolysis of hydroxides?

A

Oxygen.

34
Q

What reaction always happens at the cathode?

A

Reduction.

35
Q

What reaction always happens at the anode?

A

Oxidation.

AS Chemistry (44 decks)

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