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Edexcel Electrolysis - GCSE Physics > Half Equations and terminology > Flashcards

Half Equations and terminology Flashcards

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1
Q

Copper (II) chloride solution electrolysis - anode reaction?

A

2Cl– (aq) → Cl2 (g) + 2e–

This is oxidation

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2
Q

Copper (II) chloride solution electrolysis - cathode reaction?

A

Cu2+ (aq) + 2e– → Cu (s)

This is reduction

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3
Q

Sodium chloride solution electrolysis - anode reaction?

A

2Cl– → Cl2 (g) + 2e–

This is oxidation

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4
Q

Sodium chloride solution electrolysis - cathode reaction?

A

2H+ (aq) + 2e– → H2 (g)

This is reduction

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5
Q

Sodium sulfate solution electrolysis - anode reaction?

A

O2- (aq) → O2 (g) + 2e–

This is oxidation

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6
Q

Sodium sulfate solution electrolysis - cathode reaction?

A

2H+ (aq) + 2e– → H2 (g)

This is reduction

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7
Q

Water acidified with sulphuric acid electrolysis - anode reaction?

A

2O2- (aq) → O2 (g) + 4e–

This is oxidation

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8
Q

Water acidified with sulphuric acid electrolysis - cathode reaction?

A

2H+ (aq) + 2e– → H2 (g)

This is reduction

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9
Q

Molten lead bromide electrolysis - anode reaction?

A

2Br– (l) → Br2 (g) + 2e–

This is oxidation

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10
Q

Molten lead bromide electrolysis - cathode reaction?

A

Pb2+ (l) + 2e– → Pb (l)

This is reduction

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11
Q

Copper (II) chloride solution electrolysis - what is formed at the anode?

A

Chlorine gas

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12
Q

Copper (II) chloride solution electrolysis - what is formed at the cathode?

A 
Copper metal (deposited on the cathode)
It is a brown / pink colour
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13
Q

Sodium chloride solution electrolysis - what is formed at the anode?

A

Chlorine gas

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14
Q

Sodium chloride solution electrolysis - what is formed at the cathode?

A

Hydrogen gas

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15
Q

Sodium sulfate solution electrolysis - what is formed at the anode?

A

Oxygen gas

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16
Q

Sodium sulfate solution electrolysis - what is formed at the cathode?

A

Hydrogen gas

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17
Q

Water acidified with sulphuric acid electrolysis - what is formed at the anode?

A

Oxygen gas

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18
Q

Water acidified with sulphuric acid electrolysis - what is formed at the cathode?

A

Hydrogen gas

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19
Q

Molten lead bromide electrolysis - what is formed at the anode?

A

Bubbles of bromine gas

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20
Q

Molten lead bromide electrolysis - what is formed at the cathode?

A

Lead metal

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21
Q

What does PANIC stand for?

A 
Positive
Anode
Negative
Is
Cathode
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22
Q

What does OILRIG stand for?

A 
Oxidation is a
Loss of Electrons
Reduction
Is a
Gain of Electrons
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23
Q

What is the name of the liquid in an electrolysis cell?

A

The electrolyte

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24
Q

What are the anode and cathode called together?

What are they usually made of?

A

The electrodes

They are usually made of carbon / graphite, but are made of copper when purifying copper (electrolysis of copper sulfate solution).

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25
Q

Is the cathode positive or negative?

A

Negative

26
Q

Is the anode positive or negative?

A

Positive

27
Q

Which Ionic compounds will conduct electricity?

A

Only ionic compounds that are molten (heated to melt) or dissolved in solution will conduct electricity.
This means that ions can move and transfer the current.

28
Q

Will any covalent compounds conduct electricity?

A

Only graphite, since it has free electrons

29
Q

How can we make lead molten?

A

By heating it to melt the lead

30
Q

How do we know if hydrogen or a metal forms at the negative cathode?

A

Hydrogen gas is only produced at the cathode if the metal is more reactive than hydrogen (e.g. sodium with sodium sulphate electrolysis).

Copper is less reactive than hydrogen, so is produced at the anode (e.g. with copper (II) chloride electrolysis).

31
Q

What is the test for carbon dioxide gas?

A

Turns limewater milky

32
Q

What is the test for oxygen gas?

A

Relights a glowing splint

33
Q

What is the test for hydrogen gas?

A

Squeaky pop test

34
Q

What is the test for chlorine gas?

A

Red litmus turns blue and is then bleached white

35
Q

Which ions are involved in the electrolysis of copper (II) chloride solution?

A 
Positive = Cu2+   and     H+
Negative = Cl-   and   OH-
36
Q

Which ions are involved in the electrolysis of sodium chloride solution?

A 
Positive = Na+    and     H+
Negative = Cl-   and   OH-
37
Q

Which ions are involved in the electrolysis of sodium sulfate solution?

A 
Positive = Na+    and     H+
Negative = SO4 2-    and   OH-
38
Q

Which ions are involved in the electrolysis of water acidified with sulphuric acid?

A 
Positive = H+
Negative = SO4 2-    and   OH-
39
Q

Which ions are involved in the electrolysis of molten lead bromide?

A 
Positive = Pb2+
Negative = Br-
40
Q

What does inert mean (when talking about the electrodes)?

A

Unreactive

41
Q

What does REDOX stand for?

A

RED - uction

and

OX - idation

42
Q

Which metal is usually extracted from its ores using electrolysis?

A

Aluminium

43
Q

Why is aluminium extracted from its ores using electrolysis?

A

Because aluminium is too reactive to extract by using carbon to displace it from its ore

44
Q

What is aluminium ore (bauxite) mixed with to reduce the cost of its electrolysis

A

It is mixed with molten Cryolite.

45
Q

Give two reasons why cryolite is used in the electrolysis of aluminium oxide.

A

The mixture of cryolite and aluminium oxide has a lower melting point than pure aluminium oxide.

This means a lower amount of energy is required to establish effective conditions for electrolysis and thus makes it more cost effective.

46
Q

What is the name of aluminium ore?

A

bauxite

47
Q

Where do positively charged cations migrate during electrolysis?

A

They move towards the oppositely / negatively charged cathode

48
Q

Where do negatively charged anions migrate during electrolysis?

A

They move towards the oppositely / positively charged anode

49
Q

What are electrolytes?

A

Electrolytes are ionic compounds in the molten state or dissolved in water

50
Q

Define electrolysis

A

A process in which electrical energy, from a direct current supply, decomposes electrolytes

51
Q

What are the electrodes made of during the purification of copper in the electrolysis of copper sulfate solution?

A

The electrodes are made of copper

52
Q

EXAM QUESTION:

Zinc can be extracted from its ore by electrolysis or by heating the ore with carbon. Give a reason for the actual method that is used. (1 mark)

A

Heating with carbon is used since it is cheaper than using electrolysis.

53
Q

EXAM QUESTION:

Identify the products formed at the anode and cathode when molten potassium iodide is electrolysed. (2 marks)

A

Iodine at the anode

Potassium at the cathode

54
Q

EXAM QUESTION:

Copper is purified by the electrolysis of copper sulfate solution using an impure copper anode and a pure copper cathode.

Write the half-equation for the formation of a copper atom from a copper ion. (2 marks)

A

Cu2+ +2e- → Cu

55
Q

EXAM QUESTION:

When a solution of sodium sulfate, Na2SO4, is electrolysed, the products formed at the electrodes are hydrogen and oxygen.

Explain the formation of the products at the electrodes.
(4 marks)

A

Hydrogen (H+) and sodium (Na+) ions attracted to the cathode

Hydroxide (OH−) ions and sulfate (SO42−) ions attracted to the anode

Since the ions are attracted to the oppositely charged
electrode

2H+ (aq) + 2e– → H2 (g)

O2- (aq) → O2 (g) + 2e–

56
Q

EXAM QUESTION:

Which material is most suitable to make the electrodes for the electrolysis of a dilute acid?

A) zinc
B) sulfur
C) iron
D) graphite

(1 mark)

A

D) Graphite

57
Q

EXAM QUESTION:

State what is meant by the term electrolyte (2 marks)

A

A substance that conducts electricity (1)

When molten or in aqueous solution (1)

58
Q

EXAM QUESTION:

Copper sulfate solution was electrolysed for five minutes using copper electrodes.

Here are the results:

anode mass BEFORE electrolysis = 1.16g
anode mass AFTER electrolysis = 0.85g

cathode mass before electrolysis = 1.28g
cathode mass after electrolysis = 1.57g

Calculate the mass of copper deposited.

A

Copper is deposited on the cathode

Mass deposited = 1.57 – 1.28

                       = 0.29g
59
Q

Which two ions does water dissociate into?

A

OH - and H+ ions

60
Q

What do bubbles mean in electrolysis?

A

A gas is being produced

61
Q

Define reduction

A

Reduction is a gain of electrons

Reduction is also a loss of oxygen

62
Q

Define oxidation

A

Oxidation is a loss of electrons

Oxidation is also a gain of oxygen

Edexcel Electrolysis - GCSE Physics (1 decks)

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