DP Chemistry (first assessment 2025)
Question 19M.1A.SL.TZ1.5
| Date | May 2019 | Marks available | [Maximum mark: 1] | Reference code | 19M.1A.SL.TZ1.5 |
| Level | SL | Paper | 1A | Time zone | TZ1 |
| Command term | Question number | 5 | Adapted from | N/A |
5.
[Maximum mark: 1]
19M.1A.SL.TZ1.5
Bromine consists of two stable isotopes that exist in approximately a 1 : 1 ratio. The relative atomic mass, Ar, of bromine is 79.90. Which are the stable isotopes of bromine?
A. 79Br and 81Br
B. 80Br and 81Br
C. 78Br and 80Br
D. 79Br and 80Br
[1]
Markscheme
A
Examiners report
Almost 56 % of candidates could find a 1:1 ratio as an average of 2 items, however many had 79Br and 80Br with an average mass of 79.90
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.