Question 1
The Lewis formula of phosphorus trichloride, PCl₃, is shown. What is the shape of the molecule?
Chemistry grade boundaries explained
Boundaries are set after each session against grade descriptors, so they change every session. They apply to your weighted total.
| Scale | 1 to 7 in each subject |
|---|---|
| Weighting | Paper 1 36%, Paper 2 44%, scientific investigation 20% |
| May results | On the candidate website from 12.00 GMT on 6 July |
| Your boundaries | Your coordinator may show you the lower and upper boundary of your grade |
After results day
- Grades appear on candidates.ibo.org.
- If your school allows, you see your total and your grade's boundaries.
- A re-mark costs a fee and needs your written consent: a grade can go down.
Try 2 questions
Question 2
| Run | Initial reading / cm³ | Final reading / cm³ | Titre / cm³ |
|---|---|---|---|
| Rough | 0.00 | 23.60 | 23.60 |
| 1 | 0.20 | 23.30 | 23.10 |
| 2 | 0.50 | 23.95 | 23.45 |
| 3 | 1.00 | 24.15 | 23.15 |
A student records the titres in the table. Concordant titres agree within 0.10 cm³. Which mean titre should be used to calculate the concentration?
Next step
Questions people ask
Are grade boundaries the same every year?
No. The IB sets them each session.
Can a re-mark lower my grade?
Yes, which is why your written consent is needed.