Electrolysis

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What is a cation?
A positively charged ion that would be attracted to the cathode during electrolysis
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What is an anion?
A negatively charged ion that would be attracted to the anode.
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What is the positive electrode?
The anode
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What is the negative electrode?
The cathode
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What is oxidation?
Loss of electrons
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What is reduction?
Gain of electrons
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What always forms positive ions?
Metals
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Why can solid ionic compounds not conduct electricity?
Because the ions cannot move throughout the entire structure and therefore cannot conduct electricity
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What is the electrolyte?
The substance decomposed by electrolysis
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What fundamentally occurs during electrolysis?
Electrolysis breaks down a substance using electricity. Positively charged cations move towards the cathode (negative electrode) and at the same time negatively charged anions move towards the anode (positive electrode)
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What are the electrodes often made of?
Inert substances such as graphite, so that the electrodes do not react
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In what state can ionic compounds be electrolysed?
When they are either molten or dissolved in water, because their ions are free to move an can carry their charge to the electrodes.
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What happens when the ions reach the electrode?
They either lose or gain electrons, depending upon their charge
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What is a redox reaction?
One in which both oxidation and reduction take place
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What happens during electrolysis of molten compounds.
1)The positive metal ions migrate towards the cathode (neg.), gain an electron, then metal is deposited. 2)Negative non-metal ions migrate to the anode (pos) and lose an electron and are then released (oft. gas)
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What happens during electrolysis of compounds in solution at the negative electrode?
If the metal is low in the reactivity series/less reactive than hydrogen, it is deposited. If it is more reactive than hydrogen/high in the reactivity series, it will remain as an ion. If solution= mixture of metal ions, least reactive is deposited
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What happens during electrolysis of compounds in solution at the positive electrode?
If the compound contains a halide ion (Cl-, Br-), it will give up its electrons and release the halogen as a diatomic molecule (Cl2). 2) If compound does not contain a halide ion, oxygen is formed
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What is the test for oxygen?
It relights a glowing splint
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What is the test for hydrogen?
A lighted spill goes "pop"
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What is the test for chlorine?
Bleaches litmus paper.
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Name some properties of aluminium.
1)Light 2)Strong 3)Resistant to corrosion 4)Recyclable 5)Conductor (It is also very abundant)
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Where do we get aluminium from.
Bauxite ore (bauxite contains mainly aluminium oxide), that is purified to aluminium oxide, which is the electrolysed to form pure aluminium.
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How do chemists solve the problem of aluminium oxide having a very high boiling point?
Aluminium oxide has a very high boiling point (2050 degrees) so it is mixed with cryolite. The molten mixture can be electrolysed at 850 degrees
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What is the cathode during the electrolysis of aluminium oxide?
The cathode (negative electrode) is the carbon lining of the cell. Aluminium ions are reduced here to form aluminium atoms.
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How is Aluminium separated after being reduced?
It is denser than cryolite, so sinks to the bottom and is funnelled away as a pure liquid metal
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What happens at the anode during electrolysis of aluminium?
The anode is made out of carbon. Oxygen is oxidised at the anode to form oxygen atoms, which bond in pairs to form molecules of O2 gas. The oxygen reacts with the hot carbon anode to form carbon dioxide. Therefore the anode need replacing regularly.
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What is brine?
Solution of water containing highly concentrated sodium chloride
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What are the products of electrolysis of brine?
1) Sodium hydroxide solution 2)Hydrogen gas 3)Chlorine gas
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During electrolysis of brine, where is chlorine formed?
At the anode.
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What forms at the cathode during electrolysis of brine?
Hydrogen, (sodium is also attracted to the cathode, however, it more reactive that hydrogen, so hydrogen is discharged)
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What is left once the chlorine gas and the hydrogen gas have been discharged during the electrolysis of brine?
Sodium hydroxide solution
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What uses does chlorine have?
Important in the production of disinfectants. When it is mixed with sodium hydroxide, it makes bleach.
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What uses does hydrogen have?
Margarine is produced when hydrogen is reacted with vegetable oils
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What uses does sodium hydroxide have?
Used as an alkali in industry. Also used to make soap and paper as well as bleach
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What is electroplating?
An electroplated object is coated with a thin layer of a metal by electrolysis
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Suggest some reasons for electroplating?
1)Protect metal beneath it corroding 2)Making jewellery more inexpensive 3)Increase resistance of a substance
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Explain the set up of electroplating.
The object that we want to electroplate is put in place of the cathode and the plating metal is put in place of the anode. The electrolyte must contain ions of the plating material
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Other cards in this set

Card 2

Front

What is an anion?

Back

A negatively charged ion that would be attracted to the anode.

Card 3

Front

What is the positive electrode?

Back

Preview of the front of card 3

Card 4

Front

What is the negative electrode?

Back

Preview of the front of card 4

Card 5

Front

What is oxidation?

Back

Preview of the front of card 5
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