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Chemistry > Electrolysis > Flashcards

Electrolysis Flashcards

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1
Q

What is electrolysis?

A

Electrolysis is the process of passing an electric current through a substance and bringing about a chemical reaction, which is a decomposition reaction.

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2
Q

What is an electrolyte?

A

A substance that conducts an electric current when molten or dissolved in water (aqueous) with chemical reactions at the electrodes.

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3
Q

How is the current passed in electrolysis?

A

Ions carry the current in the molten liquid or aqueous solution, or electrons carry the current in the wires.

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4
Q

What are electrodes?

A

Electrodes are pieces of metal or carbon (in the form of graphite, a conductor) through which the current enters and leaves the electrolyte.

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5
Q

What is a cathode?

A

The cathode is the negative electrode, joined to the negative terminal of the battery.

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6
Q

What is the anode?

A

The anode is the positive electrode, joined to the positive terminal of the battery.

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7
Q

What direction do the electrons flow in electrolysis?

A

Electrons flow from the anode through the power supply to the cathode.

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8
Q

What are the two types of electrodes?

A

Unreactive (inert) electrodes and reactive (non-inert) electrodes.

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9
Q

What happens to the ions in electrolysis using inert electrodes?

A
  1. Positive ions (cations) from the electrolyte are attracted to the negative electrode and gain electrons (are reduced)
  2. Negative ions (anions) from the electrolyte are attracted to the positive electrode and lose electrons (are oxidised)
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10
Q

In the electrolysis of molten compounds, what happens at the cathode?

A

Metal ions gain electrons, forming a metal.

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11
Q

In electrolysis of molten compounds, what happens at the anode?

A

Non-metal ions lose electrons, forming a non-metal (usually a diatomic molecule)

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12
Q

What is an industrial application of electrolysis of molten compounds?

A

The extraction of aluminium.

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13
Q

What is the main ore of aluminium which is changed into Aluminium oxide before electrolysis?

A

Bauxite.

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14
Q

Why is the aluminium oxide dissolved into molten Cryolite?

A

As it reduces its boiling point and thus reduces energy costs and improves the electrical conductivity of the electrolyte.

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15
Q

In the electrolysis of aqueous compounds, what forms at the cathode?

A

Either a metal or hydrogen forms (which ever is least reactive)

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16
Q

In the electrolysis of aqueous compounds, what forms at the anode?

A

A non-metal form (other than hydrogen) usually what is the SIMPLEST ION (eg. Cl- is simpler that NO3 2-). Note: a concentrated halide solution will always give a halogen but a dilutive halide solution or a non-halide solution, will give oxygen from hydroxide ions.

17
Q

What is a industrial application of electrolysis of aqueous compounds?

A

The electrolysis of concentrated aqueous sodium chloride.

18
Q

What Ions are present in the electrolysis of a aqueous sodium chloride?

A

Na+, Cl-, H+, OH-

19
Q

What are the uses of chlorine (a product from the electrolysis of aqueous sodium chloride)?

A

Treating drinking water, for making bleach and plastics such as PVC

20
Q

What are the uses of hydrogen (a product of the electrolysis of aqueous sodium chloride)?

A

It is used in the Haber process (The manufacture of ammonia)

21
Q

What are the uses of sodium hydroxide (a product of the electrolysis of aqueous sodium chloride)?

A

To make soaps.

22
Q

In electrolysis using non-inert electrodes, what reaction happens at the anode?

A

Metal atoms lose electrons at the anode and become metal ions (anode dissolves and wears away)

23
Q

In electrolysis using non-Inert electrodes, what reaction happens at the cathode?

A

Metal ions gain electrons at the cathode and become metal atoms (cathode builds up)

24
Q

What is a common use of electrolysis using non-inert electrodes?

A

The purification of metals, such as copper.

25
Q

In the purification of copper,what is at the anode?

A

A block of impure metal.

26
Q

In the purification of copper, what is at the cathode?

A

A thin piece of pure metal.

27
Q

What is the electrolyte in the purification of copper?

A

Copper sulphate

28
Q

What happenes to the impurities in the purification of copper?

A

They are left as anode slime/mud

29
Q

What are reasons for electroplating using non-inert electrodes?

A

To make things look better (appearance) or for protection from corrosion and abrasion.

30
Q

What is placed at each electrode when electroplating by electrolysis?

A

The metal to be plated is placed at the cathode, and the metal used for plating is placed at the anode.

31
Q

What is a conductor?

A

Substances that let electricity pass through them.

32
Q

What dictates whether electricity can pass through a substance?

A

If a substance contains charged particles (electrons or ions) that are free to move, then electricity can pass through it: the moving particles carry the electric current.

33
Q

What are the most commonly used metals cables?

A

Copper and aluminium.

34
Q

What are the reasons for using copper in wires?

A

It is a very good conductor of electricity, easily drawn into thin wires (ductile), easily purified.

35
Q

What are the reasons for using aluminium in wires?

A

It is a good conductor of electricity, resists corrosion, low-density so higher diameter cables can be used thus reducing resistance while reducing the risk of sagging (aluminium cables also have a steel core which further reduces the risk of Sagging and breaking)

36
Q

What are the most commonly used insulators?

A

Plastics e.g. PVC and ceramics

37
Q

What are the reasons that plastics are often used as insulators?

A

They do not conduct electricity: have high melting points so they can be used at high temperatures, not affected by water or oxygen, can be moulded into complex shapes.

Chemistry (84 decks)

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