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emma- lamda > Electrolysis > Flashcards

Electrolysis Flashcards

1
Q

What are acids?

A

Substances that produces hydrogen ions when they are added to water

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2
Q

What is made when a solution is dissolved in water?

A

An aqueous solution

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3
Q

What ph do acids have?

A

Ph values of less than 7

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4
Q

What does the state symbol aq mean?

A

The ions are in an aqueous solution

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5
Q

Hydrogen ions make solutions ……….

A

Acidic

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6
Q

What are bases?

A

Things that react with acids and neutralise them

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7
Q

What are alkalis?

A

Bases that have dissolved in water to make alkaline solutions

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8
Q

What ions do alkalis produce in the solution?

A

Hydroxide ions

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9
Q

What is the PH of alkalis?

A

Values greater than 7

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10
Q

What ph will strong acids have?

A

Low ph, such as values between 0-2

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11
Q

What ph values will highly alkaline solutions have?

A

12-14

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12
Q

What do indicators do?

A

Change colour based on the ph of solutions

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13
Q

Which indicators can tell us the ph of a solution?

A

Universal indicators or full range indicators

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14
Q

Which metals will acids react with?

A

Ones above hydrogen in the reactivity series

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15
Q

Why are the reactions of very reactive metals and acids too dangerous to be done safely?

A

They are too violent

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16
Q

When metals react with an acid what is produced?

A

A salt and hydrogen gas.

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17
Q

What type of compound are metal oxides and metal hydroxides?

A

Bases

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18
Q

What happens when an acid reacts with a base?

A

Neutralisation occurs

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19
Q

What are the products of neutralisation?

A

Salt and water

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20
Q

What is the formula of hydrochloride acid?

A

HCL

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21
Q

What is the formula of sulphuric acid?

A

H2SO4

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22
Q

What is the formula of nitric acid?

A

HNO3

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23
Q

How is the soluble salt obtained from an base/metal that is insoluble in water + acid reaction?

A
  • metals/base that is insoluble In Water is added little at time til all the acid has reacted
  • filter the mixture to remove excess solid reactant leaving a salt solution
  • it is left to crystallise leaving the salt
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24
Q

How can soluble salts be made?

A

By reacting an acid and alkali

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25
Q

How can we represent the reaction between any acid and alkali?

A

H+(aq) + OH-(aq) ——-> H2O (l)

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26
Q

How can the salt be obtained from a neutralisation reaction?

A
  • the alkali is added little at time til all the acid has
  • there is no visible change so indicator must be used to detect when the reactions complete
  • the exact measurements of acid and alkali must be recorded
  • repeat the experiment without the indicator
  • it is left to crystallise leaving the salt
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27
Q

What are ammonium salts used as?

A

Fertilisers

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28
Q

How can insoluble salts be made?

A

Mixing solutions of soluble salts

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29
Q

How can the insoluble salts be obtained from the mixture of soluble salt solutions?

A 
Mix the 2 solutions
A precipitate forms
The solution is filtered
Washed
And left to dry
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30
Q

What is precipitate!

A

An insoluble solid formed by a reaction taking place in solution

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31
Q

What are precipitation reactions useful for?

A

Pollutants such as metal ions can be removed from water

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32
Q

How is precipitation used to remove metal pollutants from water?

A

The water is treated by adding substances that react with the pollutant metal ions dissolved in the water to form insoluble salts

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33
Q

Zinc carbonate is insoluble in water. What would happen when sodium carbonate solution is added to zinc sulphate solution?

A

Zinc carbonate would be produced as a precipitate or solid, sodium sulphate would remain in the solution

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34
Q

What is ammonium solution?

A

An alkali that does not contain metal

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35
Q

What ammonium solution react with acid what is formed?

A

Ammonium salts such as NH4NO3

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36
Q

What is electrolysis?

A

The process of breaking substances into smaller substances using electricity

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37
Q

Why can electrolysis not take place on solids?

A

The ions are not free to move

38
Q

Which substances can electrolysis take place on?

A

Molten ionic compounds or a solution containing ions

39
Q

What is the substance that is broken down by electrolysis called?

A

Electrolyte

40
Q

What must happen to ionic compounds before they can be electrolysed?

A

Melted or dissolved in water

41
Q

What must the electrodes be made from?

A

Inert substances that do not react with the products

42
Q

What happens to the ions in the electrolyte do in electrolysis?

A

They move to the electrodes where they are discharged to produce elements

43
Q

Which electrode do positively charged ions go?

A

Negative electrode, where they form metals or hydrogen depending on the ions in the electrolyte

44
Q

Which electrode do negatively charged ions go?

A

Positive electrode where they lose their charge to form non- metallic elements

45
Q

Molten zinc chloride is electrolysed. Name the substances formed at the positive and negative electrodes

A

+ chlorine

- zinc

46
Q

What happens when the positively charged ions reach the negative electrode?

A

Gain electrons to become neutral atoms

47
Q

What is reduction?

A

Gaining electrons

48
Q

Positive ions are …… In electrolysis

A

Reduced

49
Q

Ions with a single positive charge gain …. And those with …. Gain 2 electrons

A

1

2+

50
Q

What happens at the positive electrode in electrolysis?

A

The negative ions lose electrons to become neutral atoms

51
Q

What is oxidation?

A

Lose of electrons

52
Q

What do non-metals Ions form in electrolysis?

A

Non-metal atoms combine to form molecules

53
Q

Complete the half equation for the formation of chlorine at a positive electrode
2CL- —–> ….. + …..

A

CL2 + 2E-

54
Q

What does water contain?

A

Hydrogen ions and hydroxide ions

55
Q

When a solution is electrolysed using water as an electrolyte what may be produced at the negative electrode and when?

A

If the positive ions in the solution are those of a metal more reactive than hydrogen, hydrogen will be produced

56
Q

What could be produced at the positive electrode from an aqueous solution?

A

Oxygen

57
Q

If a solution contains a reasonably of a halide ion what will be produced at the positive electrode?

A

A halogen will be produced

58
Q

What are halide ions?

A

Chlorine, bromine, iodine

59
Q

Name the products at the positive and negative when aqueous copper sulphate solution is electrolysed using carbon electrodes.

A

+ oxygen

- copper

60
Q

What ph is pure water?

A

Neutral, ph 7

61
Q

Why does aluminium have to be extracted from its ore by electrolysis?

A

It is more reactive than carbon

62
Q

What does aluminiums ore contain?

A

Aluminium oxide

63
Q

Why is aluminium oxide mixed with cryolite?

A

Means the mixture can be electrolysed at a lower temperature saving energy, making it less expensive

64
Q

What does the electrolysis of aluminium produce?

A

Aluminium and oxygen

65
Q

What happens at the negative electrode in the electrolysis of aluminium?

A

The aluminium ions are reduced to aluminium atoms by gaining electrons.

66
Q

What happens at the positive electrode in the electrolysis of aluminium?

A

The oxide ions are oxidised to oxygen atoms by losing electrons and the oxygen atoms from oxygen molecules

67
Q

Why do the positive carbon electrodes have to be replaced over time?

A

At the high temperatures of the cell the oxygen reacts with the carbon electrodes to produce carbon dioxide so they gradually burn away

68
Q

What is brine?

A

A solution of sodium chloride in water

69
Q

What ions does brine contain?

A

Sodium, chloride, hydrogen and hydroxide ions

70
Q

When brine is electrolysed what is produced at the negative electrode?

A

Hydrogen from the hydrogen ions

71
Q

When brine is electrolysed what is produced at the positive electrode?

A

Chlorine from the chloride ions

72
Q

What solution is left after the electrolysis of brine?

A

Sodium hydroxide, sodium and hydroxide ions

73
Q

Why is hydrogen produced when sodium chloride solution is electrolysed?

A

The solution contains hydrogen ions which are discharged in the preference of sodium ions

74
Q

Half equation at the positive electrode in brine

A

2cl- —> cl2 + 2e-

75
Q

Half equation at the negative electrode IN Brine

A

2H+ + 2e- —-> H2

76
Q

What is sodium hydroxide used for?

A

It is a strong alkali and is used for soap, bleaching paper

77
Q

What is chlorine used for?

A

Kill bacteria in drinking water and swimming pools

78
Q

What is hydrogen used to make?

A

Margarine and hydrochloride acid

79
Q

Why is the electrolysis of brine important?

A

It produces 3 useful products

80
Q

What is electroplating?

A

Using electrolysis to out a thin coat of metal onto an object

81
Q

Which metals are often used in plating?

A

Gold, silver, chromium

82
Q

Why is electroplating done?

A

Make it more attractive
Protect metal from corrosion
Increase hardness
Reduce costs by using thin layer instead of pure metal

83
Q

In electroplating which object is used as the negative electrode?

A

The object to be plated

84
Q

In electroplating what object is the positive electrode?

A

The plating metal

85
Q

What is the electrolyte like for electroplating?

A

It’s a solution containing. Ions of the plating metal

86
Q

What happens at the positive electrode in electroplating?

A

Atoms of the plating metal lose electrons to form metal atoms which go into the solution

87
Q

What happens at the negative electrode in electroplating?

A

Metal ions from the solution gain electrons to form metal atoms which are deposited to the object to be plated

88
Q

Half equation nickel electroplating positive electrode

A

Ni —–> Ni2+ + 2e-

Ni2+ + 2e- —–> Ni

89
Q

Describe how you would silver plate a piece of copper jewellery

A

Pass electricity through a cell with the item of jewellery as the negative electrode, the positive electrode being silver and containing a solution of a silver salt (eg silver nitrate solution, as the electrolyte)

90
Q

For writing half equations which elements natural exist in pairs (diatomic molecules)

A 
Hydrogen 
Chlorine
Florine 
Nitrogen
Oxygen 
Iodine 
Bromine
91
Q

What is an electrolyte?

A

A liquid containing free moving ions The substance that is broken down by electricity in electrolysis

emma- lamda (5 decks)

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