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Science (chemistry) > C6- Electrolysis > Flashcards

C6- Electrolysis Flashcards

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1
Q

Electrolysis

A

Breaking down ionic compounds using electricity

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2
Q

Electrolyte

A

The ionic compound broken down (solution)

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3
Q

Why cant the electrolyte be a solid?

A

This is because the ions in a solid are not free to move due to the strong electrostatic forces of attraction ( and if not free then electricity doesn’t flow)

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4
Q

Whats the cathode?

A

The negative electrode

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5
Q

Whats the anode?

A

The positive electrode

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6
Q

What are the electrodes made off?

A

Carbon

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7
Q

What happens at the anode?

A

Oxidations

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8
Q

What happens at the cathode?

A

Reduction

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9
Q

Whats aluminium useful for?

A

Pans, cooking foil, aeroplanes, drink cans, car bodies, bicycle frames…

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10
Q

Whats the name of Aluminium’s metal ore?

A

Bauxite

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11
Q

Whats the aluminium oxide mixed with for electrolysis?

A

Molten cryolite

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12
Q

Why is aluminium oxide mixed with molten cryolite?

A

To lower the melting point and this will reduce the amount of energy needed and save money

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13
Q

Whats forms at the cathode when Aluminium is electrolysed?

A

Aluminium

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14
Q

What forms at the Anode when aluminium is electrolysed ?

A

Oxygen

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15
Q

Whats the half equation for the reaction at the Cathode ( electrolysis of aluminium)?

A

AL3+(L)+ 3e- —— -> AL(L)

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16
Q

Whats the half equation for the reaction at the Anode ( electrolysis of aluminium)?

A

2O2- (L) ——-> O2 (g) + 4e-

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17
Q

Why do the carbon anodes have to be replaced regularly (electrolysis of aluminium)

A

Because they regularly burn away as the oxygen reacts with the carbon anodes forming carbon dioxide gas

18
Q

During electrolysis of aqueous solutions where the H+ and OH- ions come from?

A

When the water breaks down

19
Q

During electrolysis of aqueous solutions what forms at the cathode?

A

The less reactive element between the positive ions ( either hydrogen or the metal) you use the reactivity series

20
Q

During electrolysis of aqueous solutions what forms at the anode?

A

OH- (hydroxide) is given off unless the electrolyte id a solution of a halide (group 7) if so a halogen is given off

Halide> hydroxide> all other negative charged ions

21
Q

What is brine?

A

concentrated sodium chloride solution

22
Q

What is the word equation for the electrolysis of brine (sodium chloride solution)?

A

Sodium chloride solution —> hydrogen gas+ chlorine gas+ sodium hydroxide solution

23
Q

What forms at the cathode during the electrolysis of brine?

A

Hydrogen (H+) ions gain 1 electron (reduced). The hydrogen atoms bond together in pairs and give off hydrogen gas

24
Q

What forms at the anode during the electrolysis of brine?

A

Chlorine atoms lose 1 electron (oxidised). The chlorine atoms bind together in pairs and give ofd chlorine gas

25
Q

Whats the half equation at the cathode during the electrolysis of brine (sodium chloride solution)?

A

2H+(aq) + 2e- ——> H2(little 2 not a charge)

26
Q

Whats the half equation at the anode during the electrolysis of brine (sodium chloride solution)?

A

2CL- (aq) —–> CL2 +2e-

27
Q

Whats the lab test for chlorine gas ?

A

Bleaches damp litmus paper white

28
Q

Whats the lab test for hydrogen gas?

A

Squeaky ‘pop’ with lighted splint

29
Q

Whats the lab test for oxygen ?

A

Relights glowing splint

30
Q

Name 3 control variables/ precautions when investigating the electrolysis of a solution?

A
  • don’t let the 2 electrodes touch each other as a short circuit would be produce pd
  • wear gloves and eye protection
  • use a lid to ensure the gas doesn’t escape
  • pay close attention to gases being produces as the volume of them will be very small
31
Q

What are the observations and element formed at the Anode during the electrolysis of copper (II) chloride?

A

Bubbles, chlorine

32
Q

What are the observations and element formed at the Cathode during the electrolysis of copper (II) chloride?

A

Colour change, copper

33
Q

What are the observations and element formed at the Anode during the electrolysis of copper (II) sulfate?

A

Bubbles ,oxygen

34
Q

What are the observations and element formed at the Cathode during the electrolysis of copper (II) sulphate?

A

Colour change, copper

35
Q

What are the observations and element formed at the Anode during the electrolysis of sodium chloride?

A

Bubbles, chlorine

36
Q

What are the observations and element formed at the Cathode during the electrolysis of sodium chloride?

A

Bubbles, hydrogen

37
Q

What are the observations and element formed at the Anode during the electrolysis of sodium sulfate?

A

Bubbles, oxygen

38
Q

What are the observations and element formed at the Cathode during the electrolysis of sodium sulfate ?

A

Bubble, hydrogen

39
Q

Explain why carbon electrodes can conducted electricty

A

It has delocolised electrons that are free to move throughout the structure

40
Q

Whats the half equation at cathode in the electrolysis of lead bromide?

A

Pb—–> Pb2+ + 2e-

41
Q

Whats the half equation at anode in the electrolysis of lead bromide?

A

2Br- + 2e- ——–> 2Br-

Science (chemistry) (6 decks)

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