Markscheme- OCR AS Level Chemistry A: Depth in chemistry- Component H032/02

GCE

Chemistry A

H432/02: Synthesis and analytical techniques Advanced GCE

Mark Scheme for November 2020

Oxford Cambridge and RSA Examinations

OCR (Oxford Cambridge and RSA) is a leading UK awarding body, providing a wide range of qualifications to meet the needs of candidates of all ages and abilities. OCR qualifications include AS/A Levels, Diplomas, GCSEs, Cambridge Nationals, Cambridge Technicals, Functional Skills, Key Skills, Entry Level qualifications, NVQs and vocational qualifications in areas such as IT, business, languages, teaching/training, administration and secretarial skills. It is also responsible for developing new specifications to meet national requirements and the needs of students and teachers. OCR is a not-for-profit organisation; any surplus made is invested back into the establishment to help towards the development of qualifications and support, which keep pace with the changing needs of today's society. This mark scheme is published as an aid to teachers and students, to indicate the requirements of the examination. It shows the basis on which marks were awarded by examiners. It does not indicate the details of the discussions which took place at an examiners' meeting before marking commenced. All examiners are instructed that alternative correct answers and unexpected approaches in candidates' scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated. Mark schemes should be read in conjunction with the published question papers and the report on the examination. ? OCR 2020

Oxford Cambridge and RSA Examinations

1. Annotations available in RM Assessor

Annotation

Meaning Correct response

Incorrect response

Omission mark

Benefit of doubt given

Contradiction

Rounding error

Error in number of significant figures

Error carried forward

Level 1

Level 2

Level 3

Benefit of doubt not given

Noted but no credit given

Ignore

2. Abbreviations, annotations and conventions used in the detailed Mark Scheme (to include abbreviations and subject-specific conventions).

Annotation DO NOT ALLOW

IGNORE ALLOW

( ) __ ECF AW ORA

Meaning Answers which are not worthy of credit Statements which are irrelevant Answers that can be accepted Words which are not essential to gain credit Underlined words must be present in answer to score a mark Error carried forward Alternative wording Or reverse argument

H432/02 1. Subject-specific Marking Instructions

Mark Scheme

November 2020

INTRODUCTION Your first task as an Examiner is to become thoroughly familiar with the material on which the examination depends. This material includes: ? the specification, especially the assessment objectives ? the question paper ? the mark scheme.

You should ensure that you have copies of these materials.

You should ensure also that you are familiar with the administrative procedures related to the marking process. These are set out in the OCR booklet Instructions for Examiners. If you are examining for the first time, please read carefully Appendix 5 Introduction to Script Marking: Notes for New Examiners.

Please ask for help or guidance whenever you need it. Your first point of contact is your Team Leader.

4

H432/02

SECTION A

Question 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Answer

A B A C D D A C D C A A A B C

Mark Scheme

Marks

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

AO element

1.2 1.1 1.1 2.3 1.2 2.1 1.1 2.2 1.2 2.5 2.6 2.2 1.1 2.3 1.2

ALLOW 5

November 2020 Guidance

5

H432/02

Mark Scheme

November 2020

SECTION B

Question

Answer

16 (a) (i) 2-bromo-3,3-dimethylbutane

Marks

AO element

Guidance

1

1.2 IGNORE lack of hyphens or addition of commas

ALLOW 3,3-dimethyl-2-bromobutane

(b) (i) Stereoisomers Same structural formula

AND Different arrangement (of atoms) in space

OR different spatial arrangement (of atoms) AND

Type: Optical

DO NOT ALLOW

2-bromo-3-dimethylbutane

methy for methyl

methly for methyl

brom for bromo

1

1.2 ALLOW structure/displayed/skeletal formula

DO NOT ALLOW same empirical formula OR same general formula

IGNORE same molecular formula IGNORE references to chiral molecules/compounds

(ii) One 3D structure with correct groups attached to the chiral C

Two 3D structures of (CH3)3CCHBrCH3 that are mirror images AND correct connectivity in both

Br

Br

(CH3)3C

C CH3 H

H3C C H

C(CH3)3

2

2.5 ALLOW small slip in one of the groups OR use of

C4H9

3D structures must have four central bonds with at

1.2 least two wedges.

For bond into paper accept:

ALLOW two 3D structures with 2 groups swapped e.g.

H432/02 Question

Answer

(c) Initiation Br2 2Br?

Propagation

+ Br?

Mark Scheme

Marks

AO element

November 2020

Guidance

Br

Br

(CH3)3C

C CH3

H

C

H3C

C(CH3)3 H

3

ALLOW Br2 Br? + Br?

IGNORE dots for initiation step,

1.2 i.e. ALLOW Br2 Br + Br OR Br2 2Br

+ HBr

DOT REQUIRED at correct position on chain.

2.5?2

ALLOW 1 mark if both propagation equations are correct by atom but dot(s) missing or on incorrect

C in chain

ALLOW 1 mark if both propagation equations are correct including position of dot(s) but structures

are not shown using skeletal formula

ALLOW ECF from incorrect intermediate

7

 ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download