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GCSE CCEA Chemistry unit 2 And 3 > Electrochemistry > Flashcards

Electrochemistry Flashcards

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1
Q

What is Electrolysis? (3)

A
  • The decomposition
  • of electrolytes
  • using electricity
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2
Q

What are Electrolytes (3)

A
  • An ionic liquid or solution
  • that conducts electricity
  • and is decomposed during electrolysis
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3
Q

What is the name of a positive electrode?

A

Anode

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4
Q

What is the name of a negative electrode?

A

Cathode

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5
Q

What is the pneumonic for remembering the charge of each electrode?

A

Positive electrode
Anode
Negative
Is
Cathode

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6
Q

Why is heat applied to an electrolyte during electrolysis? (2)

A

In order to change the
- solid ionic compound into a liquid
- where the ions are free to move and carry a charge

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7
Q

Give two half equations which demonstrate electrolysis in

LiCl

A
  • Li+ + e- —> Li
  • 2Cl- —> Cl2 + 2e-
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8
Q

What state are metals after electrolysis generally?

A

Liquid, usually a grey colour as well

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9
Q

What electrode are anions and cations attracted to?

A
  1. anion (negative ion) - anode (positive electrode)
    An-an
  2. cation (positive ion) - Cathode (negative electrode)
    Cat-cat

In both cases:
- both are oppositely charged
- electrostatic attraction pulls them together

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10
Q

What is the common name for aluminium ore?

A

Bauxite

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11
Q

When do Metals require electrolysis to extract

A

If they are more reactive than carbon, or react with carbon

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12
Q

In the electrolysis of Lithium Chloride, what electrode are the Li+ and Cl- ions attracted to?

A
  • Li+ —> Cathode
  • Cl- —> Anode
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13
Q

Give 2 Reasons electrolysis requires lots of energy

A
  • To melt the compound
  • to produce the electrical current
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14
Q

What is the Mixture used in electrolysis of aluminium

A
  • Cryolite
  • Aluminium oxide
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15
Q

What apparatus is used in the electrolysis of Lead Bromide and Lithium Chloride (7)

A
  • a power source
  • evaporating basin or crucible
  • tripod
  • gauze
  • heat source
  • bulb on negative side of circuit
  • the actual electrolyte
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16
Q

Why is Cryolite added to bauxite?

A
  • To lower the melting point of aluminium oxide and
  • increase its electrical conductivity
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17
Q

Why is there a bulb in the circuit of electrolysis equipment?

A

If the circuit is complete, the bulb lights up

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18
Q

What is The material of the anode for aluminium extraction

A

Graphite

19
Q

Why does the anode require regular replacement in aluminium extraction (2)

A
  • high temp causes
  • Oxygen produced at the anode, to react with graphite (CO2 formed) in the anode, wearing it away
20
Q

What type of reaction is the electrolysis of lithium chloride?

A

Redox:

  • lithium gains electron - reduction
  • chloride ions lose electrons - oxidation
21
Q

What is formed at the anode by aluminium extraction

A

Oxygen

22
Q

What is formed at the cathode by aluminium extraction

A

Molten aluminium

23
Q

What are the observations at the anode in the electrolysis of lithium chloride?

A
  • yellow-green gas
  • pungent smell
24
Q

How do you recycle Aluminium (4)

A
  • Shred
  • remove coating
  • melt
  • cast (into ingots)
25
Q

What is the observation at the cathode in the electrolysis of lithium chloride?

A

Molten grey liquid

26
Q

What are the Advantages of recycling Aluminium (give 2)

A
  • Reduces the energy required - cheaper
  • aluminium is a finite resource - prevents waste from going to landfill
  • better for the environment:
    1. does not involve mining methods
    2. Less greenhouse gas emissions through energy production
27
Q

In the electrolysis of Lead Bromide, what electrode are the Pb2+ and Br- ions attracted to?

A
  • Pb2+ —> cathode
  • Br- —> anode
28
Q

What type of reaction is the electrolysis of lead bromide?

A

Redox:
- lead gains electrons- reduction
- bromide ions lose electrons - oxidation

29
Q

What are the observations at the anode in the electrolysis of lead bromide?

A
  • red-brown gas
  • pungent smell
30
Q

What is the observation at the cathode in the electrolysis of lead bromide?

A

Molten grey liquid drops formed

31
Q

What functions as the cathode in the electrolysis of bauxite?

A

The graphite lining of the container

32
Q

Where does the aluminium go after the electrolysis of bauxite (2)

A
  • sinks to the bottom of the container
  • is tapped off
33
Q

In the electrolysis of dilute sulphuric acid what are the products formed at the anode

A

Oxygen and water

34
Q

In the electrolysis of dilute sulphuric acid what is the product formed at the cathode

A

Hydrogen

35
Q

What happens to the sulphate ion in the electrolysis of H2SO4

A

It is unchanged

36
Q

In the electrolysis of dilute sulphuric acid, what electrode are the H+ and OH- and SO4- ions attracted to?

A
  • H+ —> Cathode
  • OH- and SO4-—> Anode
37
Q

What happens to the OH- ion in the electrolysis of H2SO4

A

It is preferentially discharged

38
Q

What is the half equation at the anode in the electrolysis of H2SO4

A

4OH- —> O2 + 2H2O + 4e-

39
Q

What is the half equation at the cathode in the electrolysis of H2SO4

A

H2 —> 2H+ + 2e-

40
Q

What type of reaction is the electrolysis of sulfuric acid?

A

Redox:

  • H+ ions gain electrons - reduction
  • OH- ions lose electrons - oxidation
41
Q

What is preferential discharge? (2)

A
  • if more than one type of ion is attracted towards a particular electrode
  • the one discharged is the ion that requires the least energy
42
Q

Why is graphite used for electrodes? (3)

A
  • relatively inert
  • high m.p.
  • conducts electricity
43
Q

Why does an electrolyte need to be an ionic compound that’s molten or in solution?

A

So the ions can move and carry a charge

44
Q

What happens to electrolytes when they conduct electricity?

A

They decompose

GCSE CCEA Chemistry unit 2 And 3 (10 decks)

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