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Chemistry > C6 Electrolysis > Flashcards

C6 Electrolysis Flashcards

(56 cards)

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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

Study These Flashcards
A

Extract reactive metals

Electrolysis of brine

Purifying copper

24
Q

Why hydrogen is produced at the negative electrode and not sodium

Study These Flashcards
A

Hydrogen is less reactive than sodium

25
Which ion gave pH of 1
Hydrogen ions
26
Name the type of bond between the hydrogen and the chlorine atoms in a molecule of hydrogen chloride
Covalent
27
What happens to the concentration of the sulphuric acid as the electricity is passed through it
Concentration increases
28
Phytomining/phytoextraction
Uses plants to absorb metal compounds from the ground through their roots
29
Bioleaching
Use bacteria to break down low-grade ores to produce acidic solution
30
Polyatomic ion
Group of covalently bonded atoms that carries a net charge
31
Electrolyte
Liquid or solution that contains ions and can conduct electricity
32
Why do solid ionic compounds not conduct electricity
Ions cannot move
33
What products are always formed at the anode
OH- and negative element like Cl-
34
What products are always formed at the cathode
H+ and positive element like Na+
35
Cathode
Negative electrode
36
Anode
Positive electrode
37
Where are metals formed
Cathode
38
Where are non-metals formed
Anode
39
How can ionic substances be electrolysed
By melting or dissolving
40
Why can solid ionic substances not be electrolysed
They don't conduct electricity (ions can't move)
41
In electrolysis of solutions, when is the metal not produced at the cathode
When the metal is more reactive than hydrogen
42
In the electrolysis of a metal halide solution, what is produced at the anode?
Halogen
43
In the electrolysis of a metal sulfate solution, what is produced at the anode?
Oxygen
44
Half equation for ionisation of water
H2O -----> H+ + OH-
45
What metals are extracted from ionic compounds by using electrolysis
Metals that are more reactive than carbon
46
In the electrolysis of aluminum oxide what are the anodes made of
Graphite
47
In the electrolysis of aluminum oxide why do the anodes need to be replaced
They react with oxygen being formed
48
What 3 products formed from electrolysis of sodium chloride solution
Chlorine Hydrogen Sodium hydroxide
49
How is chloride formed from electrolysis
Cl- attracted to anode where they get oxidised
50
How is hydrogen formed
Hydrogen attracted to cathode where they reduced
51
How is sodium hydroxide formed
Sodium and hydroxide ions electrostatically attact to form sodium hydroxide
52
Two factors that affect the amount of a substance produced during electrolysis
Increase voltage/current increase flow of charges Increase number of charges increase rate of electrolysis
53
One disadvantage of plating iron with tin
Tim costs more and is less abudnant in Earth's crust
54
Reactivity series least reactive 5
Hydrogen Copper Silver Gold Platinum
55
Reactivity series less reactive than carbon From more reactive to less reactive
Carbon Zinc Iron Tin Lead
56
Reactivity series top 5 most reactive
Potassium Sodium Calcium Magnesium Aluminium

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