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y13 btec - unit 5 - chemistry > A1 - Extraction of Alumina and Aluminium > Flashcards

A1 - Extraction of Alumina and Aluminium Flashcards

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1
Q

What ore is Alumina extracted from?

A

Bauxite

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2
Q

What substance can be extracted from Bauxite?

A

Alumina

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3
Q

What is the name of the process used to extract alumina?

A

Bayer process

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4
Q

What is the Bayer process used for?

A

Extracting alumina from bauxite

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5
Q

Why is bauxite crushed in the Bayer process?

A

To increase the rate of reaction

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6
Q

Which step in the Bayer process increases the rate of reaction?

A

Crushing the bauxite

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7
Q

What is bauxite reacted with in the Bayer process?

A

NaOH

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8
Q

What is added to cause crystallisation during the Bayer process?

A

Al(OH)3

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9
Q

What is the formula of alumina?

A

Al2O3

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10
Q

What is the name of Al2O3?

A

Alumina

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11
Q

What ions does Al2O3 contain?

A

Al3+ and O2−

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12
Q

What is the name of the process used to extract aluminium from alumina?

A

Hall-Heroult electrolysis

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13
Q

What is the Hall-Heroult electrolysis used for?

A

Extracting aluminium from alumina

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14
Q

What is alumina dissolved in during electrolysis?

A

Molten cryolite

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15
Q

What is molten cryolite used for in the electrolysis of alumina?

A

Dissolving the alumina

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16
Q

Why is alumina dissolved instead of melted during electrolysis?

A

Alumina has a high melting point and it requires less energy (and is cheaper) to dissolve it

17
Q

Which ions go to the positive anode in the electrolysis of alumina?

A

O2−

18
Q

Which ions go to the negative cathode in the electrolysis of alumina?

A

Al3+

19
Q

Write the equation for the reaction of Al3+ at the negative electrode

A

Al3+ + 3e− → Al

20
Q

What do the Al3+ ions turn into during the electrolysis of alumina?

A

Molten aluminium

21
Q

Why does Al form at the bottom of the electrolysis cell?

A

Because the aluminium that forms is molten and sinks

22
Q

What is the positive anode made from in the electrolysis of alumina?

A

Graphite

23
Q

Write the equation for the reaction of O2− at the positive electrode

A

2O2− → O2 + e−

24
Q

What do the O2− ions turn into during the electrolysis of alumina?

A

O2

25
Q

Why do the positive graphite anodes need to be replaced regularly during the electrolysis of alumina?

A

The positive graphite anodes react with O2 produced at the anode and form CO2 gas

26
Q

What does the O2 produced at the anode do during the electrolysis of alumina?

A

React with the positive graphite anode

y13 btec - unit 5 - chemistry (9 decks)

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