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GCSE Chemistry > Chapter C6 Electrolysis > Flashcards

Chapter C6 Electrolysis Flashcards

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1
Q

What does electrolysis mean?

A

Breaking down using electricity

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2
Q

What do you do in electrolysis?

A

Use a current to break down an ionic compound

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3
Q

What is the compound called that is broken down in electrolysis?

A

The electrolyte

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4
Q

What is the posture electrode called?

A

Anode

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5
Q

What is the negative electrode called?

A

Cathode

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6
Q

What are electrodes commonly made from?

A

Unreactive substance

Such as graphite

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7
Q

Why are electrodes made from unreactive substances?

A

So electrodes do not react with the electrolyte or products made

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8
Q

What happens when the ions in electrolysis reach the electrodes?

A

Lose their charge and become elements

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9
Q

Who was the first person to work on electrolysis?

A

Michael faraday

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10
Q

Do ionic compounds conduct electricity?

A

As a solid- no as their ions are in fixed positions

As a liquid- yes as the ions can move towards the electrodes

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11
Q

Can covalent compounds undergo electrolysis?

A

Only if they from ions when reacting with water

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12
Q

What is a half equation?

A

An equation that describes reduction or oxidation

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13
Q

Do a half equation for the electrolysis of Pb

A

Pb—-> 2E- + pb^2+

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14
Q

Complete the half equation for electrons being removed from negative ions for Br

A

2br- - 2e- ——> br^2

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15
Q

Why is electrolysis more complicated in aqueous solutions?

A

Because of the ions formed by water as it ionises

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16
Q

What happens at the anode in the electrolysis of aqueous solutions?

A

Oxygen gas is given off and hydroxide ions are discharged

17
Q

What happens when a Solution contains a large concentration of halide?

A

Forms a halogen

18
Q

What happens if two elements can be formed at an electrode?

A

The less reactive one will be formed

19
Q

What is the compound electrolysed when performing electrolysis on aluminium?

A

Aluminium oxide

20
Q

What is the ore of aluminium?

A

Bauxite

21
Q

Describe the process of electrolysis of aluminium oxide?

A

The aluminium oxide requires free moving ions but the pure melting of it is very high 2050C.
So mix it with cryolite, and it melts at 850C
Aluminium forms on the cathode
Oxygen forms at the anode

22
Q

What is the equation that results in the product of aluminium oxide?

A

Aluminium oxide

——> electrolysis ——>

aluminium +oxygen

23
Q

What is brine?

A

Concentrated sodium chloride solution

24
Q

What is produced from electrolysis of brine?

A 
Chlorine gas (anode) 
Hydrogen gas (cathode) 
Sodium hydroxide
25
Q

Half equation for anode of brine?

A

2CL-

—-> electrolysis

Cl^2 + 2e-

26
Q

When electrolysis of brine occurs, why doesn’t sodium form at the cathode?

A

As hydrogen is the less reactive element and so if formed, whilst sodium remains in the aqueous solution

27
Q

How do you test the solution at the cathode?

A

Acid base indicator

28
Q

With electrolysis of aluminium oxide, why must the anode be regularly replaced?

A

As oxygen reacts with the graphite (carbon) to make carbon dioxide

29
Q

Problems with electrolysis?

A

Is expensive
To melt the ionic compounds requires lots of bond energy
A lot of energy is required to produce the electric current

30
Q

Process of aluminium electrolysis

A

Add aluminium to cryolite
Melts at 850C
Put carbon anode in water- the aluminium ions will go to the cathode, turning into aluminium atoms, whilst oxygen will be produced at the anode. This oxygen will wear at the anode, which is made of graphite, resulting in the formation of carbon dioxide. This means the anode will slowly get used up in the reaction and so must be replaced. A siphon is then used to collect the aluminium atoms

31
Q

What are the products of sodium chloride in electrolysis

A

Sodium hydroxide
Chlorine
Hydrogen

32
Q

What are the products if sodium sulfate in electrolysis

A

Hydrogen and oxygen

33
Q

What are the products of copper chloride in electrolysis

A

Chlorine gas

Copper

34
Q

What are the products of copper sulfate in electrolysis

A

Copper

Oxygen gas

35
Q

Test for hydrogen gas

A

Squeaky pop

36
Q

Test for oxygen

A

Glowing splint

37
Q

Test for chlorine gas

A

Bleaches damp litmus paper

GCSE Chemistry (9 decks)

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