Question 19M.3.hl.TZ1.4a
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.3.hl.TZ1.4a |
| Level | hl | Paper | 3 | Time zone | TZ1 |
| Command term | Outline | Question number | a | Adapted from | N/A |
Polybutadiene, used in truck tyres, is a polymer of buta-1,3-diene. The spatial arrangement of atoms in the polymer depends on the type of catalyst used.
Outline two differences between heterogeneous and homogeneous catalysts.
[2]
Any two of:
heterogeneous catalyst is in different phase than reactants AND homogeneous catalyst in same phase [✔]
homogeneous catalysts chemically change/react and reformed at end of reaction
OR
reactants adsorb onto heterogenous catalyst and products desorb [✔]
heterogeneous catalysts are more easily removed than homogenous catalysts [✔]
heterogeneous catalysts can function at higher temperatures [✔]
homogeneous catalysts are «generally» more selective [✔]
homogeneous catalysts offer a broader range of reactions [✔]
Note: Accept “state” for “phase”.
Accept “heterogeneous catalyst provides a surface to activate reaction”.
Most candidates correctly stated one difference between heterogeneous and homogeneous catalysts. Few gave a second difference even though the question is worth 2 marks.
