DP Chemistry (first assessment 2025)
Question 22M.2.HL.TZ1.5a(iii)
| Date | May 2022 | Marks available | [Maximum mark: 1] | Reference code | 22M.2.HL.TZ1.5a(iii) |
| Level | HL | Paper | 2 | Time zone | TZ1 |
| Command term | State | Question number | a(iii) | Adapted from | N/A |
a(iii).
[Maximum mark: 1]
22M.2.HL.TZ1.5a(iii)
(a(iii))
State the number of (sigma) and (pi) bonds in Compound A.
[1]
Markscheme
: 9
AND
: 1 ✔
Examiners report
Mediocre performance in stating the number of σ (sigma) and π (pi) bonds in propanone; the common answer was 3 σ and 1 π instead of 9 σ and 1 π, suggesting the three C-H σ bonds in each of the two methyl groups were ignored.
Syllabus sections
Structure 2. Models of bonding and structure » Structure 2.2—The covalent model » Structure 2.2.15—Sigma bonds σ form by the head-on combination of atomic orbitals where the electron density is concentrated along the bond axis. Pi bonds π form by the lateral combination of p-orbitals where the electron density is concentrated on opposite sides of the bond axis. Deduce the presence of sigma bonds and pi bonds in molecules and ions.