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Chemistry > C6 Electrolysis > Flashcards

C6 Electrolysis Flashcards

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1
Q

Electrolysis

A

Using electricity to break down electrolytes to form elements

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2
Q

Describe electrolysis in terms of movement of ions

A

Passing an electric current through electrolytes causes the ions to move to the electrodes

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3
Q

Why electrolysis can only occur when an ionic compound is molten or in aqueous solution

A

Ionic compounds only conduct electricity when molten or in aqueous solution

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4
Q

Word equation to describe the electrolysis of a molten ionic compound

A

Ionic compound ——> metal + non-metal

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5
Q

Describe electrolysis with half equations at the electrodes of 2NaCl ——> 2Na + Cl2

A

Cathode (reduction) - Na+ + e- ——> Na

Anode (oxidation) 2Cl- —–> Cl2 + 2e-

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6
Q

How to predict the products at each electrode for the electrolysis of a molten ionic compound

A

A metal forms at the cathode and a non-metal forms at the anode

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7
Q

How to explain the classification of the reactions at each electrode as oxidation or reduction

A

Reduction happens at the negative cathode as this is where positive ions gain electrons

Oxidation happens at the positive anode as this is where negative ions lose electrons

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8
Q

What would be produced at the anode when some solutions are electrolysed

A

Oxygen

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9
Q

Describe electrolysis of solutions in terms of movement of ions

A

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

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

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10
Q

How hydrogen ions and hydroxide ions can be present in solutions

A

Hydroxide ions float around in solution

Hydrogen ions transferred directly to a neighboring water molecule to form hydronium ions

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11
Q

What can be produced at the anode when some solutions are electrolysed

A

Hydrogen

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12
Q

Word equation to describe electrolysis of a lead bromide

A

Lead bromide + electricity → lead + bromine

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13
Q

How can aluminum be extracted from aluminum oxide

A

Using electrolysis

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14
Q

Describe the electrolysis of aluminium oxide

A

Positively charged aluminium ions gain electrons from the cathode and form molten aluminium

Oxide ions lose electrons at the anode, and form oxygen molecules

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15
Q

Why electrolysis is used to extract aluminium from compound

A

The temperatures needed are too high to be economic

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16
Q

Word equation to describe the electrolysis of aluminium oxide

A

Aluminum oxide ——-> aluminum + oxygen

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17
Q

Why electrolysis is an expensive metal extraction method

A

Cost of electricity for electrical energy

Specialized equipment can be expensive

Electrode material costs

High temperature requirements

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18
Q

Why extraction of aluminum is expensive

A

High temperature

Energy intensive

Electrode consuption

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19
Q

Why cryolite is added to aluminium oxide in the industrial extraction of aluminium

A

Reduces melting point of aluminum oxide from 2050°C to 950°C

Enhances electrical conductivity of molten mixture

Improves fluidity of mixture

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20
Q

State the products of the electrolysis of brine and a use for each

A

Sodium hydroxide and hydrogen

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21
Q

How to electrolyse brine in terms of ions moving

A

Sodium and hydrogen ions go to anode

Chlorine and hydroxide ions go to cathode

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22
Q

What are ionic compounds made from

A

Positive and negative ions

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23
Q

Industrial uses of electrolysis

A

Extract reactive metals

Electrolysis of brine

Purifying copper

24
Q

Why hydrogen is produced at the negative electrode and not sodium

A

Hydrogen is less reactive than sodium

25
Q

Which ion gave pH of 1

A

Hydrogen ions

26
Q

Name the type of bond between the hydrogen and the chlorine atoms in a molecule of hydrogen chloride

A

Covalent

27
Q

What happens to the concentration of the sulphuric acid as the electricity is passed
through it

A

Concentration increases

28
Q

Phytomining/phytoextraction

A

Uses plants to absorb metal compounds from the ground through their roots

29
Q

Bioleaching

A

Use bacteria to break down low-grade ores to produce acidic solution

30
Q

Polyatomic ion

A

Group of covalently bonded atoms that carries a net charge

31
Q

Electrolyte

A

Liquid or solution that contains ions and can conduct electricity

32
Q

Why do solid ionic compounds not conduct electricity

A

Ions cannot move

33
Q

What products are always formed at the anode

A

OH- and negative element like Cl-

34
Q

What products are always formed at the cathode

A

H+ and positive element like Na+

35
Q

Cathode

A

Negative electrode

36
Q

Anode

A

Positive electrode

37
Q

Where are metals formed

A

Cathode

38
Q

Where are non-metals formed

A

Anode

39
Q

How can ionic substances be electrolysed

A

By melting or dissolving

40
Q

Why can solid ionic substances not be electrolysed

A

They don’t conduct electricity (ions can’t move)

41
Q

In electrolysis of solutions, when is the metal not produced at the cathode

A

When the metal is more reactive than hydrogen

42
Q

In the electrolysis of a metal halide solution, what is produced at the anode?

A

Halogen

43
Q

In the electrolysis of a metal sulfate solution, what is produced at the anode?

A

Oxygen

44
Q

Half equation for ionisation of water

A

H2O —–> H+ + OH-

45
Q

What metals are extracted from ionic compounds by using electrolysis

A

Metals that are more reactive than carbon

46
Q

In the electrolysis of aluminum oxide what are the anodes made of

A

Graphite

47
Q

In the electrolysis of aluminum oxide why do the anodes need to be replaced

A

They react with oxygen being formed

48
Q

What 3 products formed from electrolysis of sodium chloride solution

A

Chlorine

Hydrogen

Sodium hydroxide

49
Q

How is chloride formed from electrolysis

A

Cl- attracted to anode where they get oxidised

50
Q

How is hydrogen formed

A

Hydrogen attracted to cathode where they reduced

51
Q

How is sodium hydroxide formed

A

Sodium and hydroxide ions electrostatically attact to form sodium hydroxide

52
Q

Two factors that affect the amount of a substance produced during electrolysis

A

Increase voltage/current increase flow of charges

Increase number of charges increase rate of electrolysis

53
Q

One disadvantage of plating iron with tin

A

Tim costs more and is less abudnant in Earth’s crust

54
Q

Reactivity series least reactive 5

A

Hydrogen
Copper
Silver
Gold
Platinum

55
Q

Reactivity series less reactive than carbon
From more reactive to less reactive

A

Carbon
Zinc
Iron
Tin
Lead

56
Q

Reactivity series top 5 most reactive

A

Potassium
Sodium
Calcium
Magnesium
Aluminium

Chemistry (10 decks)

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