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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.
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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…