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Chemistry GCSE > Electrolysis > Flashcards

Electrolysis Flashcards

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1
Q

Define Electrolytes

A

ionic compounds in a molten state or dissolved in water

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2
Q

What must the substance be to do electrolysis

A

ionic and liquid.
solids ions cannot move enough
covalent cannot as they share electrons

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3
Q

What are the negatively charged anions attracted to

A

Attracted to the positive anode

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4
Q

What are the positively charged cations attracted to

A

Attracted to the negative cathode

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5
Q

What is a pneumonic to remember electrode charges

A

PANIC

Positive Anode Negative Is Cathode

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6
Q

What is a pneumonic to remember where reduction takes place

A

REDCAT

Reduction At Cathode

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7
Q

Where are metals and non metals always formed in electrolysis

A

Metal is always formed at cathode and non-metal at anode

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8
Q

What happens in the electrolysis of molten Lead Bromine

A

Lead formed at cathode, Bromine gas formed at anode

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9
Q

What happens in the electrolysis of water

A

When water is slightly acidified it causes dissociation creating H+ and OH- ions which attract to electrodes

Hydrogen and oxygen gas formed

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10
Q

What ions does an electrolyte dissolved in water contain

A

H+ ions, OH- ions and the two ions from ionic compound

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11
Q

What happens at the anode with electrolysis in solution

A

All ions ending with -ate are not discharged but oxygen from water instead

If Halides are present then halides are discharged instead

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12
Q

What are some examples of halides

A

Diatomic molecules; Chlorine, Bromine, Iodine

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13
Q

What happens at cathode with electrolysis in solution

A

Metals more reactive than hydrogen are not discharged, metals less reactive than hydrogen are discharged

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14
Q

What is the equation for production of oxygen from water

A

4OH- - 4e- –> O2 + 2H2O

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15
Q

What happens if the anode is carbon and oxygen is produced

A

Anodes have to be replaced frequently as CO2 is produced e.g. production of aluminium oxide

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16
Q

What is a half equation

A

represent the reaction that happens at an electrode during electrolysis. It shows what happens when ions gain or lose electrons

17
Q

What are the rules of a half equation

A
  • electrons are shown as e-
  • the numbers of atoms of each element must be the same on both sides
  • the total charge on each side must be the same (usually zero)
18
Q

What is the solution left behind for electrolysis of copper using graphite electrodes

A

Dilute sulphuric acid

19
Q

What is the solution left behind for purification of copper using copper electrodes

A

Copper sulphate

20
Q

What are the anode and cathode made of in purification of copper

A

Anode is impure copper and cathode is pure copper

21
Q

How is sludge formed during purification of copper

A

From the impurities of the impure copper anode

22
Q

What happens to the anode and cathode in purification of copper

A

During electrolysis, the anode loses mass as copper dissolves, and the cathode gains mass as copper is deposited.

23
Q

What are the half equations for purification of copper

A

Cathode: Cu2+ + 2e- –> Cu

Anode : Cu –> Cu2+ + 2e-

24
Q

What is electroplating

A

Coating objects with a thin layer of metal using electrolysis

25
Q

What should be the negative cathode when electroplating

A

Negative cathode is the object to be electroplated

26
Q

What should be the positive anode when electroplating

A

Positive anode should be the metal that you want to coat the object with

27
Q

What should be the electrolyte when electroplating

A

solution of the coating metal

28
Q

How do you electroplate a spoon with silver

A

a metal spoon, is connected to the negative terminal of the power supply. A piece of silver is connected to the positive terminal. The electrolyte is silver nitrate solution.

29
Q

what is used to lower the melting point of aluminium oxide

A

aluminium oxide dissolved in cryolite

30
Q

What are the electrodes made in purification of aluminium oxide

A

graphite

31
Q

What happens at anode and cathode during electrolysis of aluminium oxide

A

Aluminium reduced at cathode then topped off

Oxygen produced at anode to make oxygen gas

32
Q

Why do positive electrodes need to be replaced frequently

A

As oxygen is being produced at anode so it reacts with graphite electrodes so CO2 produced

33
Q

Important factors when choosing aluminium extraction points

A
  • in close proximity to a power station, in order to provide the large supply of electricity
  • near the coast to allow for materials import
  • near roads and railway lines to allow for product transport
  • near a town or city for workers to live by
  • away from built-up areas, so that the noise and pollution of the site do not affect the local population

Chemistry GCSE (8 decks)

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