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Chemistry > Electrolysis > Flashcards

Electrolysis Flashcards

1
Q

Explain what is electrolysis

A

If you pass on electric current through an ionic substance thats molten or in a solution it breaks down into the elements it’s made of this is electrolysis

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2
Q

What does electrolysis require to conduct electricity?

A

It requires a liquid to conduct electricity called the electrolyte

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3
Q

What do electrolytes contain?

A

Electrolytes contain free ions . They are usually the molten or dissolved ionic substance

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4
Q

What happens during electrolysis?

A

Electrons are taken away from ions at the positive electrode and given to other are ions at the negative electrode

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5
Q

What does electrolysis reactions involve?

A

Oxidation
And
Reduction

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6
Q

What is reduction?

A

Reduction is the gain of electrons

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7
Q

What is oxidation?

A

Oxidation is the loss of electrons

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8
Q

What does OIL RIG stand for

A

Oxidation
Is
Loss

Reduction
Is
Gain

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9
Q

When will a salt conduct electricity?

A

When it is molten

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10
Q

What does electrolysis mean?

A

Electrolysis is the splitting up with electricity

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11
Q

When common salt is dissolved in water and electrolysed what three useful products are made?

A

Hydrogen , chlorine and sodium hydroxide

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12
Q

What is the name of the positive and the negative electrodes?

A

Positive - anode

Negative - cathode

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13
Q

At which electrode do ions lose electrons through oxidation?

A

The Anode

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14
Q

At which electrode do ions gain electrons through reduction?

A

The cathode

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15
Q

What are the two useful products of the electrolysis of sodium chloride solution used in industry?

A

1) chlorine has many uses such as bleach and plastics

2) sodium hydroxide is a very strong alkali which is used in the chemical industry such as to make soap

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16
Q

How is electrolysis used with aluminium?

A

Electrolysis is used to remove aluminium from its ore

17
Q

What is aluminium is ore called?

A

Bauxite

18
Q

What is cryolite used to do?

A

Cryolite is used to lower the temperature (and costs)

19
Q

What is aluminium and cryolite used to do together and why?

A

Aluminium oxide is dissolved in molten cryolite because aluminium oxide has a very high melting point of over 2000°C which would be very expensive to melt

20
Q

Which electrodes are aluminium and oxygen formed at?

A

Aluminium forms at the negative electrode is an oxygen forms at the positive electrode

21
Q

What does it mean when oxygen reacts with carbon in the electrode to produce carbon dioxide ?

A

This means that the positive electrode is gradually getting away and has to be replaced every now and again

22
Q

What is electroplating?

A

Electroplating coats one metal onto the surface of another

23
Q

When electroplating which electrode do you put the metal object you want to plate and the pure metal you want it to be played with

A

The negative electrode is the metal object you want to plate

The positive electrode is the pure metal you want it to be plated with

24
Q

How would you electroplate silver onto a Brass cup?

A

You would make the brass cup of the negative electrode (to attract the positive silver ions). Then you would make a lump of silver the positive electrode. Then you would dip them in a solution of silver ions (e.g silver nitrate)

25
Q

What are the two different uses for electroplating?

A
  • decoration

- conduction

26
Q

In electroplating how is decoration a useful property?

A

Silver is attractive but expensive.
It’s much cheaper to plate a brass cup with silver than it is to make the cup out of solid silver but it looks just as pretty

27
Q

How is conduction a useful property for electroplating?

A

Metals like copper conduct electricity well . Because of this they’re often used to plate metals for electronic circuits and computers.

28
Q

What state must an ionic compound be in if it’s to be used as an electrolyte?

A

It must be molten or dissolved in water

29
Q

In electrolysis what is meant by the terms oxidation and reduction

A

Oxidation is loss of electrons and reduction is the gain of electrons

30
Q

At which electrode are metals deposited during electrolysis?

A

At the negative electrode

31
Q

During the electrolysis of molten lead bromide, which gas is produced at the positive electrode?

A

Bromine

32
Q

An object requires electroplating. Which electrode should it be used as?

A

The negative electrode

33
Q

During electrolysis what is the name of the gas produced at the negative electrode?

A

Hydrogen

34
Q

State the half equation for the reaction of the negative electrode when hydrogen is produced…

A

2H+ + 2e- –> H2

35
Q

What is the name of the gas produced at the positive electrode during electrolysis of a sodium chlorine solution?

A

Chlorine

36
Q

Suggest one use for the gas produced at the positive electrode (chlorine)

A

The production of bleach or plastic bags

37
Q

Explain why aluminium oxide is dissolved in molten cryolite (2)

A

To lower the temperature that electrolysis can take place at. This makes it cheaper

38
Q

Explain why sodium hydroxide is left in the solution at the end of the reaction (3)

A

Sodium is more reactive than hydrogen, so sodium ions stay in solution. Hydroxide ions from water are also left behind. This means that sodium hydroxide is left in the solution.

39
Q

The positive electrode is made out of carbon explain why it is needed to be replaced over time

A

Oxygen is made at the positive electrode. The Oxygen will react with the carbon in the electrode to make carbon dioxide. This will gradually wear the electrode away

Chemistry (11 decks)

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