DP Chemistry (first assessment 2025)

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Question 21M.1A.SL.TZ1.5

Date	May 2021	Marks available	[Maximum mark: 1]	Reference code	21M.1A.SL.TZ1.5
Level	SL	Paper	1A	Time zone	TZ1
Command term	Derive	Question number	5	Adapted from	N/A

5.

[Maximum mark: 1]

21M.1A.SL.TZ1.5

What is the relative molecular mass of bromine, according to the following mass spectrum?

NIST Mass Spectrometry Data Center Collection © 2014 copyright by the U.S. Secretary of Commerce
on behalf of the United States of America. All rights reserved.

A. $\frac{158 \times 52 + 160 \times 100 + 162 \times 48}{52 + 100 + 48}$

B. $\frac{158 \times 52 + 160 \times 100 + 162 \times 48}{158 + 160 + 162}$

C. $\frac{79 \times 11 + 81 \times 11 + 158 \times 52 + 160 \times 100 + 162 \times 48}{11 + 11 + 52 + 100 + 48}$

D. $\frac{79 \times 11 + 81 \times 11}{11 + 11}$

[1]

Markscheme

A

Syllabus sections

Structure 1. Models of the particulate nature of matter » Structure 1.2—The nuclear atom » Structure 1.2.3—Mass spectra. Mass spectra are used to determine the relative atomic masses of elements from their isotopic composition. Interpret mass spectra in terms of identity and relative abundance of isotopes.