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AS CHEMISTRY 7404/2 Paper 2 Organic and Physical Chemistry Mark scheme June 2021.

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AS CHEMISTRY 7404/2 Paper 2 Organic and Physical Chemistry Mark scheme June 2021. MARK SCHEME – AS CHEMISTRY – 7404/2 – JUNE 2021 11 Question Marking guidance Additional Comments/Guidelines Mark 01.1 Number of molecules (with a particular energy) Ignore particles / atoms Allow amount or fraction or proportion for number 1 Question Marking guidance Additional Comments/Guidelines Mark 01.2 There are no molecules with no energy All molecules / particles have some energy Allow particles / atoms 1 Question Marking guidance Additional Comments/Guidelines Mark 01.3 Most probable / common / modal energy 1 Question Marking guidance Additional Comments/Guidelines Mark 01.4 M1 Peak should be at same energy (i.e. in line with X) M2 Overall area should be half the original area; after diverging from the origin, the second line should not touch the first line M1 and M2 marked independently M2 area should be about half of the original 1 1 MARK SCHEME – AS CHEMISTRY – 7404/2 – JUNE 2021 12 Question Marking guidance Additional Comments/Guidelines Mark 02.1 M1 electrophilic addition M2 must show an arrow from the double bond towards a Br atom in a Br–Br molecule M3 must show the breaking of the Br–Br bond M4 is for the structure of the correct carbocation M5 must show an arrow from the lone pair of electrons on the Br– towards the positively charged atom of their carbocation All arrows are double-headed. Penalise one mark from the total for M2-5 if half headed arrows are used. Do not penalise the “correct” use of “sticks” Penalise only once in any part of the mechanism for a line and two dots to show a bond M2 ignore partial negative charges on the double bond M3 penalise incorrect partial charges on the Br–Br bond and penalise formal charges Penalise M4 if there is a bond drawn to the positive charge Max 3 of 4 marks (M2-5) for wrong organic reactant or wrong carbocation (ignore structure of product) For M5, credit attack on a partially positively charged carbocation structure, but penalise M4 for the structure of the carbocation 1 1 1 1 1 Question Marking guidance Additional Comments/Guidelines Mark 02.2 M1 C=C electron rich / area of high electron density M2 Br-Br becomes polarised M3 δ+ Br attracted to C=C M1 ignore idea that C=C is negative or highly electronegative 1 1 1.

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AS
CHEMISTRY
7404/2
Paper 2 Organic and Physical Chemistry
Mark scheme
June 2021
Version: 1.0 Final




*216A74042/MS*

, MARK SCHEME – AS CHEMISTRY – 7404/2 – JUNE 2021



Mark schemes are prepared by the Lead Assessment Writer and considered, together with the relevant
questions, by a panel of subject teachers. This mark scheme includes any amendments made at the
standardisation events which all associates participate in and is the scheme which was used by them in
this examination. The standardisation process ensures that the mark scheme covers the students’
responses to questions and that every associate understands and applies it in the same correct way.
As preparation for standardisation each associate analyses a number of students’ scripts. Alternative
answers not already covered by the mark scheme are discussed and legislated for. If, after the
standardisation process, associates encounter unusual answers which have not been raised they are
required to refer these to the Lead Examiner.

It must be stressed that a mark scheme is a working document, in many cases further developed and
expanded on the basis of students’ 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.


Further copies of this mark scheme are available from aqa.org.uk




Copyright information

AQA retains the copyright on all its publications. However, registered schools/colleges for AQA are permitted to copy material from this booklet for their own
internal use, with the following important exception: AQA cannot give permission to schools/colleges to photocopy any material that is acknowledged to a third
party even for internal use within the centre.

Copyright © 2021 AQA and its licensors. All rights reserved.


2

, MARK SCHEME – AS CHEMISTRY – 7404/2 – JUNE 2021



AS and A-Level Chemistry
Mark Scheme Instructions for Examiners
1. General
The mark scheme for each question shows:
• the marks available for each part of the question
• the total marks available for the question
• the typical answer or answers which are expected
• extra information to help the examiner make his or her judgement and help to delineate what is
acceptable or not worthy of credit or, in discursive answers, to give an overview of the area in
which a mark or marks may be awarded.
The extra information in the ‘Comments’ column is aligned to the appropriate answer in the left-
hand part of the mark scheme and should only be applied to that item in the mark scheme.
You should mark according to the contents of the mark scheme. If you are in any doubt about
applying the mark scheme to a particular response, consult your Team Leader.
At the beginning of a part of a question a reminder may be given, for example: where
consequential marking needs to be considered in a calculation; or the answer may be on the
diagram or at a different place on the script.
In general the right-hand side of the mark scheme is there to provide those extra details which
might confuse the main part of the mark scheme yet may be helpful in ensuring that marking is
straightforward and consistent.
The use of M1, M2, M3 etc in the right-hand column refers to the marking points in the order in
which they appear in the mark scheme. So, M1 refers to the first marking point, M2 the second
marking point etc.


2. Emboldening
2.1 In a list of acceptable answers where more than one mark is available ‘any two from’ is
used, with the number of marks emboldened. Each of the following bullet points is a
potential mark.
2.2 A bold and is used to indicate that both parts of the answer are required to award the
mark.
2.3 Alternative answers acceptable for a mark are indicated by the use of OR. Different terms
in the mark scheme are shown by a / ; eg allow smooth / free movement.

3. Marking points
3.1 Marking of lists
This applies to questions requiring a set number of responses, but for which students
have provided extra responses. The general ‘List’ principle to be followed in such a
situation is that ‘right + wrong = wrong’.
Each error / contradiction negates each correct response. So, if the number of error /
contradictions equals or exceeds the number of marks available for the question, no
marks can be awarded.
However, responses considered to be neutral (often prefaced by ‘Ignore’ in the mark
scheme) are not penalised.



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