Question 19M.3.HL.TZ1.9a.i
| Date | May 2019 | Marks available | [Maximum mark: 1] | Reference code | 19M.3.HL.TZ1.9a.i |
| Level | HL | Paper | 3 | Time zone | TZ1 |
| Command term | Estimate | Question number | a.i | Adapted from | N/A |
Discs were soaked in different antibiotics and were placed on a culture of Bacillus subtilis spread on sterile agar in a Petri dish. The Petri dish was left in an incubator, after which zones of inhibition were observed surrounding some of the discs. The photograph is to scale.
[Source: Tasha L. Sturm. 2009. Kirby-Bauer disk diffusion susceptibility test. Visual Resources. American Society for
Microbiology, Washington, DC. www.microbelibrary.org Accessed 29 September 2014]
Estimate the diameter of the zone of inhibition of chloramphenicol.
[1]
16 mm or 1.6 cm ✔
units required
Allow 15 mm to 17 mm, or 1.5 cm to 1.7 cm
Although this question was correctly answered by the majority of students, there were students who found it difficult, possibly because they did not bring a ruler to the examination. Students should also be reminded to use SI units only. Measurements in inches are not acceptable.
