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Chemistry GCSE > Electrolysis > Flashcards

Electrolysis Flashcards

1
Q

What is cryolite

A

It is added to lower the melting point of the Aluminium oxide and save energy

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2
Q

Which is the positive electrode

A

Anode

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3
Q

Which is negative electrode

A

Cathode

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4
Q

What properties of aluminium make it suitable for it to be used as overhead power cables

A

They are good electrical conductors

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5
Q

Positive ions go to…

A
  • the Cathode which is the negative electrode
  • because opposite charges attract
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6
Q

Negative ions go to…

A
  • Anode which is the positive electrode
  • because opposite charges attract
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7
Q

Why can’t aluminium be extracted from its ore by reduction with carbon

A

Aluminium is more reactive than the carbon

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8
Q

How does the use of cryolite during electrolysis help reduce energy costs

A

Cryolite lowers the melting point of the Aluminium oxide (purified bauxite)

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9
Q

What’s the word equation for the reaction that results in the anode wearing away

A

Carbon + oxygen —> Carbon Dioxide

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10
Q

What’s the symbol equation for the breakdown of aluminium oxide during electrolysis

A
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11
Q

Which substance is produced at the anode during the breakdown of aluminium oxide

A

Oxygen

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12
Q

Which substance is produced at the cathode during the breakdown of aluminium oxide

A

Aluminium

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13
Q

Why is the extraction of aluminium an expensive process

A

A lot of heat is required to melt the bauxite and big electrical current

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14
Q

Why do oxide ions collect at the anode

A
  • Oxide ions have a negative charge and attract to the anodes that have a positive charge
  • This is because opposite charges attract
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15
Q

Why must the anode be replaced regularly

A
  • oxygen react with carbon anode
  • This makes CO2 gas which diffuses away
  • the reaction slowly wears away the anode
  • so it needs to be replaced
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16
Q

What can be done to conserve natural resources of aluminium

A

Recycling

17
Q

Aluminium is used for..

A
  • planes
  • car body parts
  • bikes
  • cans
18
Q

The main ore of aluminium is ….

A

Bauxite

19
Q

Electrolysis is

A
  • Using electrical energy to split up an ionic compound
  • (note that ionic compound has to be molten or dissolved in water so ions can move)
20
Q

What is the electrolite

A

Anything that’s having electrolysis happening to it

21
Q

What happens at negative electrode

A
  • it gets electrons pumped out
  • these then attract the positive metal ions
  • it doesn’t really want it’s electrons back so it takes a lot of energy
22
Q

What’s happening at the positive electrode

A
  • it is positively charged
  • attracts the negatively charged non-metal ions
  • electrons return to the battery
  • gases are formed (in pairs)
23
Q

Metals collect at the…

A

Cathode

24
Q

Write a half equation for Mg

A

Mg^2+ + 2e^- —> Mg

25
Q

Does oxidation or reduction take place at the positive electrode

A
  • oxidation
  • because it is losing an electron and oxidation is loss
26
Q

How do we know what is formed at the negative electrode

A
  • Are they less reactive than hydrogen? (Must say this to get mark)
  • They are Au, Ag, Cu, Pt. (Think what can make Jewellery)
27
Q

How do we know what forms at the positive electrode

A

1st: halide ions (group 7)
2nd: hydroxide
Never = sulfate, nitrate etc… (they remain in solution) <— remember to say this

28
Q

What is formed in Copper II chloride solution

A

Negative electrode: attracts Cu2+, H+
- Cu because it is less reactive than hydrogen
- we can see copper metal and blue colour of solution fade

Positive electrode: attracts Cl-, OH-
- Cl because it is a halide ion
- we can see bubbles and it bleaches damp indicator paper

29
Q

What is formed in Copper II sulfate solution

A

the negative electrode: attracts Cu2+, H+
- Cu formed because it is less reactive than hydrogen
- we can see copper metal and blue colour of solution fades

The positive electrode: attracts So4^2-, and OH-
- we get equation4OH^- - 4e^- —> O2 + 2H20
- you see bubbles, you can test for it by relighting a glowing splint

30
Q

What is formed in sodium chloride solution

A

Negative electrode: attracts Na+, H+
- H+ is formed because it is less reactive
- you see bubbles and test with squeaky pop

Positive electrode: attracts Cl-, OH-
- forms Cl2
- you can see bubbles and it bleaches damp indicator paper

31
Q

What is formed in sodium sulfate solution

A

At negative electrode: attracts Na+, H+
- H is formed because it is less reactive
- you see bubbles and can test with squeaky pop

At positive electrode: attracts So4^2-, OH-
- we get equation4OH^- - 4e^- —> O2 + 2H20
- you see bubbles, you can test for it by relighting a glowing splint

Chemistry GCSE (33 decks)

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