DP Chemistry (first assessment 2025)
Question 19M.2.HL.TZ2.25b
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.2.HL.TZ2.25b |
| Level | HL | Paper | 2 | Time zone | TZ2 |
| Command term | Outline | Question number | b | Adapted from | N/A |
b.
[Maximum mark: 2]
19M.2.HL.TZ2.25b
(b)
Outline the operation of a polarimeter used to distinguish between enantiomers.
[2]
Markscheme
Any two of:
«plane-» polarized light
OR
light passes through polarizer/polarizing filter [✔]
enantiomers rotate plane of «plane-» polarized light «by equal angles» in opposite directions [✔]
measure angle/direction of rotation [✔]
Examiners report
The operation of a polarimeter to distinguish between enantiomers was generally well handled by the candidates while some missed stating to measure the angle/direction of rotation.
Syllabus sections
Structure 3. Classification of matter » Structure 3.2—Functional groups: Classification of organic compounds » Structure 3.2.7—Stereoisomers have the same constitution (atom identities, connectivities and bond multiplicities) but different spatial arrangements of atoms. Describe and explain the features that give rise to cis-trans isomerism; recognize it in non-cyclic alkenes and C3 and C4 cycloalkanes. Draw stereochemical formulas showing the tetrahedral arrangement around a chiral carbon. Describe and explain a chiral carbon atom giving rise to stereoisomers with different optical properties. Recognize a pair of enantiomers as non-superimposable mirror images from 3D modelling (real or virtual).