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(GCSE) Chemistry > C6. Electrolysis (Y10 - Summer 2) > Flashcards

C6. Electrolysis (Y10 - Summer 2) Flashcards

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1
Q

🟢 What are Electrolytes

A

When an Ionic Compound is melted, the ions are free to move about within the liquid.

These liquids are able to conduct electricity and are called electrolytes.

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2
Q

🟢 What is Electrolysis

A

Electrolysis is the breaking down of the compound by the passage of electricity.

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3
Q

🟢 What are Electrodes made of?

A

They are made of carbon graphite because it has a very high melting point, and is very conductive, while also being unreactive.

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4
Q

🟢 What is the process of Electrolysis?

A

When an ionic compound is melted, the ions are free to move about within the liquid.

These liquids are able to conduct electricity and are called electrolytes.

Passing an electric current through electrolytes causes the ions to move the electrodes.

Cations (positive ions) move to the cathode and anions move to the anode. Ions are disharged at the electrodes producing elements. This peocess is called the electrolysis.

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5
Q

🟢 What is the setup for electrolysis

A

There are two electrodes, one +ve electrode (anode) and one -ve electrode cathode) that are connected through a circuit.

Electrons travel away from the anode and then into cathode, meaning the anode is positively charged and the cathode is negatively charged. This means when the ionic compound is melted, the positive ions are attracted to the cathode where they gain electrons and become atoms, while the negative ions are attracted to the anode where they lose electrons to become atoms.

This process separates parts of an ionic compound back into their original elements.

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6
Q

🟢 Electrolysis for PbBr2 (l)

What happens at the -ve electrode

A
  • You will see a grey/black deposit (all metals are grey instead of copper which is red)
  • The Pb^2+ ions will be attracted
  • Pb^2+ + 2e^- –> Pb (lead is made)
  • This means it is gains electrons, making it a reduction reaction.
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7
Q

🟢 Electrolysis for PbBr2 (l)

What happens at the +ve electrode

A
  • You will see bubbles of red-brown vapour
  • Br^- ions are attracted
  • Br^- –> 1/2Br2 + e^- (Bromine is made)
  • This means it loses electrons, meaning it is an oxidisation reaction
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8
Q

🟢 Electrolysis for NaCl (l)

What happens at the -ve electrode

A
  • You will see a grey/black deposit (all metals are grey instead of copper which is red)
  • The Na^+ ions will be attracted
  • Na^+ + e^- –> Na
  • This means it is gains electrons, making it a reduction reaction.
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9
Q

🟢 Electrolysis for NaCl (l)

What happens at the +ve electrode

A
  • You will see bubbles of yellow vapour
  • Cl^- ions are attracted
  • Cl^- –> 1/2Cl2 + e- (Chlorine is made)
  • This means it loses electrons, meaning it is an oxidisation reaction
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10
Q

🟢 Electrolysis for Al2O3 (l)

What happens at the -ve electrode

A
  • You will see a grey/black deposit (all metals are grey instead of copper which is red)
  • The Al^2+ ions will be attracted
  • Al^2+ + 2e^- –> Na
  • This means it is gains electrons, making it a reduction reaction.
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11
Q

🟢 Electrolysis for Al2O3 (l)

What happens at the +ve electrode

A
  • You will see bubbles of blue vapour
  • O^2- ions are attracted
  • O^2- –> 1/2O2 + e- (Oxygen is made)
  • This means it loses electrons, meaning it is an oxidisation reaction
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12
Q

🟢 Which ions are attracted to the positive electrode (for Cl^- for example)

A

The negative ions (Cl^-) will be attracted to the positive electrode, because positive and negative charges attract. Here, the Cl^- ions will lose an electron to form chlorine atoms.

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13
Q

🟢 Does oxidisation or reduction take place at the positive electrode (for Cl^- for example)

A

Oxidisation takes place at the psoitive electrode because the chlorine ions are losing electrons to form chlorine atoms.

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14
Q

🟢 Which ions are attracted to the negative electrode (for Mg^2+ for example)

A

The positive ions (Mg^2+) will be attracted to the negative electrode, because negative and positive charges attract. Here, the Mg^2+ ions will gain two electrons to form chlorine atoms.

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15
Q

🟢 Does oxidisation or reduction take place at the negative electrode (for Mg^2+ for example)

A

Reduction takes place at the negative electrode because the magnesium ions are gaining electrons to form magnesium atoms.

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16
Q

🟢 What is an endothermic reaction?

A

An endothermic reaction means that energy has been absorbed/taken in from the surroundings.

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17
Q

🟢 What is an exothermic reaction?

A

An exothermic reaction is When energy is transferred to the surroundings and the temperature of the surroundings increases.

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18
Q

🟢 Calcium Bromide: (Ca^2+, Br^-)

  • Formula
  • Negative Electrode Equation
  • Positive Electrode
A

Formula: CaBr2

Negative Electrode: Ca^2+ + 2e- –> Ca

Positive Electrode: 2Br^- - 2e- –> Br2

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19
Q

🟢 Iron Oxide: (Fe^3+, O^2-)

  • Formula
  • Negative Electrode Equation
  • Positive Electrode
A

Formula: Fe2O3

Negative Electrode: Fe^3+ + 3e- –> Fe

Positive Electrode: 2O^2- - 4e- –> O2

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20
Q

🟢 Explain why aluminium oxide does not conduct electricity as a solid

A

Aluminium oxide dies not conduct electricty as a solid, because all of the ions are in a giant ionic lattice, which is held tigether with strong electrostatic forces between positive and negative ions. Because the bonds are so strong as a solid, no charged ions are able to move, therefore it can’t conduct.

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21
Q

🟢 Positive Electrode attracting O2-

  • Name of electrode
  • Ions Attracted
  • Product
  • Half Equation
  • Is it an Oxidisation or Reduction Reaction
A

Name of electrode:
Anode

Ions Attracted:
Negative Ions (O^2-)
Product:
Oxygen Atoms (O2)

Half Equation:
2O^2+ - 4e- –>O2

Is it an Oxidisation or Reduction Reaction:
This is an oxidisation reaction, because it loses electrons.

22
Q

🟢 Positive Electrode attracting Al^3+:

  • Name of electrode
  • Ions Attracted
  • Product
  • Half Equation
  • Is it an Oxidisation or Reduction Reaction
A

Name of electrode:
Cathode

Ions Attracted:
Positive Ions (Al^3+)
Product:
Aluminium Atoms (Al)

Half Equation:
Al^3+ +3e- –> Al

Is it an Oxidisation or Reduction Reaction:
This is a reduction reaction because it gains electrons.

23
Q

🟢 Why is a molten mixture of aluminium oxide and cryolite rather than just molten aluminium oxide?

A

It’s a molten mixture of aluminium oxide and cryolite because it lowers the melting point of the overall substance, making the process easier and more economical.

24
Q

🟢 What are Aluminium Metals and Alloys used for

A
  • Pans
  • Overhead Power Cables
  • Aeroplanes
  • Cooking Foil
  • Drink Cans
  • Window and patio door frames
  • Bicyle frames and car bodies
25
Q

🟢 What is the overall reaction in the electrolysis cell for aluminium

A

Aluminium Oxide (electrolysis) –> (electrolysis) Aluminium + Oxygen

2Al2O3 (electrolysis) –> (electrolysis) 4Al + 3O2

Aluminium forms at the negative electrode (cathode)
Oxygen is produced at the positive electrode (anode)

26
Q

🟢 For the electrolysis of Aluminium, at the cathode (negative electrode)

A

Each aluminium ion, Al3+ gains three electrons. The ions turn into aluminium atoms. The Al3+ ions are reduced (as they gain electrons) to form Al atoms:

Al3+ (l) + 3e- –> Al (l)

The aluminium metal formed is molten at the temperature of the cell and collects at the bottom. It is siphoned or tapped off.

27
Q

🟢 For the electrolysis of Aluminium, at the anode (positive electrode)

A

Each ocide ion, O2-, loses two electrons. The ions turn into oxygen atoms. The O2- ions are oxidised (as they lose electrons) to form oxygen atoms. These bond on apirs to form molecules of oxygen as gas, O2:

2O2- (l) –> O2 (g) + 4e-

28
Q

🟢 Why is a mixture of aluminium oxide plus cryolite is used

A

Cryolite is used in order to make the melting point of aluminium oxide lower, so less energy needs to be used to extract it. This means this also costs less.

29
Q

🟢 Why has the positive electrode has to be replaced at regular intervals

A

Because the carbon reacts with the oxygen over time to make carbon dioxide. This means they need to be replaced regularly as a result.

30
Q

🟢 Why is the electrolysis of Aluminium expensive

A

Aluminium is expensive because the electrodes needs replacing regularly (as new ones need to be re-heated), and there is lots of energy costs need to melt the cryolite and generate the electricty too.

31
Q

🟢 What reactions happen at the positive and negative electrode

A

+Ve Electrode:
Negative ions are attracted and electrons are transferred away from them.

-ve Electrode
Positive ions are attracted and electrons are transferred to them.

32
Q

🟢 What happens to the liquid aluminum after is has undergone electrolysis.

A

The liquid aluminium is siphoned or tapped off out the bottom right.

33
Q

🟢 What is the equation for Acids and Alkalis and How Does Electrolysis of Aqueous Solutions work?

A

About 0.00001% of water molecules break down into H+ and OH- ions:

Equation = H2O (l) –> H+ (aq) + OH-(aq)
. (Neutral) (Concentration H+ = Concentration OH-)

These H+ and OH– ions are present in AQUEOUS solutions of ionic compounds in water and so could also be discharged.

The ions DISCHARGED when an aqueous solution is electrolysed using inert electrodes depend on the relative reactivity of the elements involved.

34
Q

🟢 What is Produced At The Cathode (Negative Electrode) in Electrolysis (substance produced, colour, and physical state)

A

At the cathode, bubbles of hydrogen gas is produced unless the metal is LESS reactive than hydrogen i.e. copper and silver.

Equation = 2H+ + 2e- –> H2 (g)

Therefore, you will see bubbles of the colourless gas Hydrogen

35
Q

🟢 What is Produced At The Anode (Positive Electrode) in Electrolysis (substance produced, colour, and physical state)

A

At the anode, oxygen is produced unless the solution contains halide ions when the halogen is produced.

For Halogens:
Equation = 2x- (aq) --> 2e- + x2    (x = a halogen)
                e.g Cl- --> Cl2
                       Br- --> Br2 
                       I- --> I2

For Hydroxide:
Equation= 4OH- –> 4e- + O2(g) + 2H2O(l)

36
Q

🟢 NaCl(aq):

  • Cations
  • Anions
  • Product at Cathode
  • Product at Anode
  • Prodcut left in Solution
A

Cations:
Na+ (aq), H+ (aq)

Anions:
Cl-

Product at Cathode:
Hydrogen, H2 (g)

Product at Anode:
Chlorine, Cl2 (g)

Product left in Solution:
Sodium Hydroxide (NaOH)
37
Q

🟢 CuSO4(aq)

  • Cations
  • Anions
  • Product at Cathode
  • Product at Anode
  • Prodcut left in Solution
A

Cations:
Cu^2+, H+

Anions:
SO4^2-

Product at Cathode:
Copper, Cu

Product at Anode:
Oxygen, O2

Product left in Solution:
Sulphuric Acid (H2SO4)
38
Q

🟢 CaBr2(aq):

  • Cations
  • Anions
  • Product at Cathode
  • Product at Anode
  • Prodcut left in Solution
A

_

Cations:
Ca^2+, H+

Anions:
Br-

Product at Cathode:
Hydrogen, H

Product at Anode:
Bromine, Br2

Product left in Solution:
Calcium Hydroxide (Ca(OH))
39
Q

🟢 AgNO3:

  • Cations
  • Anions
  • Product at Cathode
  • Product at Anode
  • Prodcut left in Solution
A

Cations:
Ag+

Anions:
NO3^-

Product at Cathode:
Silver, Ag

Product at Anode:
Oxygen, O2

Product left in Solution:
Nitric Acid (NHO3)
40
Q

🟢 H2SO4(aq):

  • Cations
  • Anions
  • Product at Cathode
  • Product at Anode
  • Prodcut left in Solution
A

Cations:
H+, H+

Anions:
SO4^2-

Product at Cathode:
Oxygen, O2

Product at Anode:
Hydrogen, H2

Product left in Solution:
Sulphuric Acid (H2SO4)
41
Q

🟢 Magnesium Bromide When Molten (MgBr2)

Negative Electrode:

  • Product
  • Half Equation
  • Oxidisation or Reduction?

Positive Electrode:

  • Product
  • Half Equation
  • Oxidisation or Reduction?
A

Negative Electrode:

  • Magnesium
  • Mg^2+ + 2e- –> Mg
  • Reduction

Positive Electrode:

  • Bromine
  • 2Br- - 2e- –> Br2
  • Oxidisation
42
Q

🟢 Magnesium Bromide When Aqueous (MgBr2)

Negative Electrode:

  • Product
  • Half Equation
  • Oxidisation or Reduction?

Positive Electrode:

  • Product
  • Half Equation
  • Oxidisation or Reduction?
A

Negative Electrode:

  • Hydrogen
  • 2H+ + 2e- –> H2
  • Reduction

Positive Electrode:

  • Bromine
  • 2Br- - 2e- –> Br2
  • Oxidisation
43
Q

🟢 Potassium Chloride When Molten (KCl)

Negative Electrode:

  • Product
  • Half Equation
  • Oxidisation or Reduction?

Positive Electrode:

  • Product
  • Half Equation
  • Oxidisation or Reduction?
A

Negative Electrode:

  • Potassium
  • K+ + e- –> K
  • Reduction

Positive Electrode:

  • Chlorine
  • 2Cl- - 2e- –> Cl2
  • Oxidisation
44
Q

🟢 Potassium Chloride When Aqueous (KCl)

Negative Electrode:

  • Product
  • Half Equation
  • Oxidisation or Reduction?

Positive Electrode:

  • Product
  • Half Equation
  • Oxidisation or Reduction?
A

Negative Electrode:

  • Hydrogen
  • 2H+ + 2e- –> H2
  • Reduction

Positive Electrode:

  • Chlorine
  • 2Cl- - 2e- –> Cl2
  • Oxidisation
45
Q

🟢 Sodium Nitrate When Aqueous (NaNO3)

Negative Electrode:

  • Product
  • Half Equation
  • Oxidisation or Reduction?

Positive Electrode:

  • Product
  • Half Equation
  • Oxidisation or Reduction?
A

Negative Electrode:

  • Hydrogen
  • 2H+ + 2e- –> H2
  • Reduction

Positive Electrode:

  • Oxygen
  • 4OH- –> 2H2O + O2 + 4e-
  • Oxidisation
46
Q

🟢 Zinc (II) Chloride When Molten (ZnCl2)

Negative Electrode:

  • Product
  • Half Equation
  • Oxidisation or Reduction?

Positive Electrode:

  • Product
  • Half Equation
  • Oxidisation or Reduction?
A

Negative Electrode:

  • Zinc
  • Zn^2+ + 2e- –> Zn
  • Reduction

Positive Electrode:

  • Chlorine
  • 2Cl- - 2e- –> Cl2
  • Oxidisation
47
Q

🟢 Is the Anode the positive or negative

A

The Anode is POSITIVE

48
Q

🟢 Is the Cathode the positive or negative

A

The Cathode is NEGATIVE

49
Q

🟢 Is a Cation Positive or Negative

A

A Cation is POSITIVE

50
Q

🟢 Is an Anion Positive or Negative

A

An Anion is NEGATIVE

(GCSE) Chemistry (24 decks)

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