OCR A LEVEL CHEMISTRY A JUNE 2025 PAPER 3 MODEL ANSWERS WORKED SOLUTIONS

Oxford Cambridge and RSA

Friday 20 June 2025 – Morning
A Level Chemistry A
H432/03 Unified chemistry
Time allowed: 1 hour 30 minutes

You must have:
* 1 8 4 9 1 6 2 3 2 2 *




• the Data Sheet for Chemistry A
You can use:
• a scientific or graphical calculator
• an HB pencil




* H 4 3 2 0 3 *




Please write clearly in black ink. Do not write in the barcodes.

Centre number Candidate number


First name(s)

Last name


INSTRUCTIONS
• Use black ink. You can use an HB pencil, but only for graphs and diagrams.
• Write your answer to each question in the space provided. If you need extra space use
the lined pages at the end of this booklet. The question numbers must be clearly shown.
• Answer all the questions.
• Where appropriate, your answer should be supported with working. Marks might be
given for using a correct method, even if your answer is wrong.

INFORMATION
• The total mark for this paper is 70.
• The marks for each question are shown in brackets [ ].
• Quality of extended response will be assessed in questions marked with an asterisk (*).
• This document has 20 pages.

ADVICE
• Read each question carefully before you start your answer.




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, 3
1 This question is about spectra.

(a) The mass spectrum for Br2 has peaks at m/z values of 79, 81, 158, 160 and 162.
The peaks at m/z 79 and 81 have virtually the same relative abundance.

(i) Complete the table to show the number of protons, neutrons and electrons in the particles that
cause the peaks at m/z 79 and 81.

Number of Number of Number of
m/z
protons neutrons electrons

79

81

[2]

(ii) Explain why there are peaks with m/z values of 158, 160 and 162 and predict their relative
abundances.

Explanation ......................................................................................................................................

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

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

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

Relative abundances .......................................................................................................................

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

..........................................................................................................................................................
[3]

(b) This question looks at proton NMR spectra of dibromoalkanes.

Predict the following.

Compound Number of peaks CH2 splitting pattern(s)

BrCH2CH2Br

BrCH2CH2CH2Br
[3]




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