DP Chemistry (first assessment 2025)
Question 19M.2.SL.TZ1.1c(i)
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.2.SL.TZ1.1c(i) |
| Level | SL | Paper | 2 | Time zone | TZ1 |
| Command term | Identify | Question number | c(i) | Adapted from | N/A |
c(i).
[Maximum mark: 2]
19M.2.SL.TZ1.1c(i)
(c(i))
Identify the initiation step of the reaction and its conditions.
[2]
Markscheme
Br2 → 2Br• [✔]
«sun»light/UV/hv
OR
high temperature [✔]
Note: Do not penalize missing radical symbol on Br.
Accept “homolytic fission of bromine” for M1.
Examiners report
Drawing or describing the homolytic fission of bromine was generally done well.
Syllabus sections
Reactivity 3. What are the mechanisms of chemical change? » Reactivity 3.3—Electron sharing reactions » Reactivity 3.3.2—Radicals are produced by homolytic fission, e.g. of halogens, in the presence of ultraviolet (UV) light or heat. Explain, including with equations, the homolytic fission of halogens, known as the initiation step in a chain reaction.