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General Certificate of Education
Chemistry 5421
CHM4
Further Physical and Inorganic
Chemistry
Mark Scheme
June examination - 2009 series
Mark schemes are prepared by the Principal Examiner and considered, together with the relevant questions, by a panel of subject teachers. This mark scheme includes any amendments made at the standardisation meeting attended by all examiners and is the scheme which was used by them in this examination. The standardisation meeting ensures that the mark scheme covers the candidates’ responses to questions and that every examiner understands and applies it in the same correct way. As preparation for the standardisation meeting each examiner analyses a number of candidates’ scripts: alternative answers not already covered by the mark scheme are discussed at the meeting and legislated for. If, after this meeting, examiners encounter unusual answers which have not been discussed at the meeting they are required to refer these to the Principal Examiner.
It must be stressed that a mark scheme is a working document, in many cases further developed and expanded on the basis of candidates’ reactions to a particular paper.
Assumptions about future mark schemes on the basis of one year’s document should be avoided; whilst the guiding principles of assessment remain constant, details will change, depending on the content of a particular examination paper.
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Chemistry - AQA GCE Mark Scheme 2009 June series
SECTION A
Q
Part
1
(a)
Sub
Part
Marking Guidance
(i)
Expt 2
Mark
1.8 × 10-3
or
8.1 × 10-5
Expt 3
6.75 k 1
Comments
If k used for the calculation: if rounded to 3.8 × 103 allow answer 1.78 × 103
or k×(2.16 × 10-8)
1
If k used for the calculation: if rounded to 3.8 × 103 allow answer 8.2 × 10-5 and if calc rounded to (3.8 × 103) (2.2× 10-8) = 8.4 ×
10-5
6.7 × 10-4
Expt 4
or √ (1.67 × 10-3 /k)
1
If k used for the calculation: if rounded to 3.8 × 103 allow answer 6.6 × 10-4
Allow 0.7 ×10-3 or 7 ×10-4
1
(a)
(ii)
k =
rate
[P][Q]2
=
1.8 × 10 -5
1
(1.2 × 10 − 3 ) (2.0 × 10 - 3 ) 2
Mark is for insertion of numbers
If upside down, score only units mark consequential on their expression for k
3750 or 3.75 × 103 or 3.8 × 103
(b)
If k is wrong, check whether apparently wrong answers in part(i) are correct conseq to wrong k.
mol-2dm6s-1
1
1
1
Any order
Horizontal straight line
1
Be generous, they need not use a ruler.
3
Chemistry - AQA GCE Mark Scheme 2009 June series
Q
2
Part
Sub
Part
Marking Guidance
The Statement : mol fraction =
(a)
Mark
mol NO2 total moles
either in this form or using their numbers, gets max 1 if answer to par (a) is wrong because of wrong no of moles (CE) of either NO2 or N2O4 or total
mol N2O4 = 1.20 - ½(0.36) = 1.0(2)
M1
total moles = 1.0(2) + 0.36 = 1.36 or 1.38 or 1.4
0.36 mol fraction of NO2 =
= 0.26
1.38
Comments
6 allow 23
M2
If AE earlier, this