Transcript PPT C2 2.7

C2 2.7 Electrolysis
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C2 2.7
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Foundation Tier- June 12, 4
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C2 2.7
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licensors. All rights reserved.
C2 2.7
•
Version 2.0
Copyright © AQA and its
licensors. All rights reserved.
C2 2.7
•
Version 2.0
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licensors. All rights reserved.
C2 2.7
•
Mark scheme- Foundation
Q
(a)(i)
(a)(ii)
(b)(i)
(b)(ii)
(b)(iii)
(c)
Answer
Extra Information
C2 2.7
Mark
Cryolite
1
Lower the melting point of the aluminium oxide
1
Opposite charges or oxide ions are negative
Attract
1
1
Carbon
1
Reacts with oxygen or forms carbon dioxide
Structure mark:
Either Al (atoms) in layers/rows
Or alloy (atoms) not in layers / rows
Accept burns
Accept Al (atoms) all the same size
Allow Al (atoms) in lines
Accept different sizes of atoms in alloy
Allow alloy (atoms) not in lines
Sliding mark:
either so (Al layers) can slide
Or so (alloy) layers cannot slide
Total
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1
1
1
8
Higher Tier June 12, 5
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C2 2.7
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licensors. All rights reserved.
C2 2.7
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Version 2.0
Copyright © AQA and its
licensors. All rights reserved.
C2 2.7
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Version 2.0
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licensors. All rights reserved.
C2 2.7
Mark scheme- Higher
•
C2 2.7
Q
Answer
Extra Information
Mark
(a)
52.9
Correct answer with or without working
= 2 marks
If answer is incorrect
Allow 2 x 27 = 54 or 27/102 x 100
Or 26.5 for 1 mark
2
(b)(i)
Because it lowers the melting point ( of the
aluminium oxide)
So less energy is needed ( to melt it)
Allow lowers the temperature needed.
Do not accept lowers boiling point
Accept so that the cell / equipment
does not melt.
1
(b)(ii)
2 O2- on left hand side
4e- on right hand side
Accept correct multiples or fractions
Accept - 4e- on left hand side
1
1
(b)(iii)
Because the electrode reacts with oxygen
or
Because the electrode burns
To form carbon dioxide or electrode made
from carbon / graphite
(411765/53 )
1
1
1
8
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C2 2.7