DP Chemistry (last assessment 2024)

Test builder »

Question 20N.3.sl.TZ0.a

Select a Test
Date November 2020 Marks available [Maximum mark: 2] Reference code 20N.3.sl.TZ0.a
Level sl Paper 3 Time zone TZ0
Command term Calculate Question number a Adapted from N/A
a.
[Maximum mark: 2]
20N.3.sl.TZ0.a

Biomagnification factor, BMF, can be defined as the concentration of a chemical, X, in a predator, relative to the concentration found in its prey.

BMF=XpredatorXprey, where X=(μg X per kg body weight)

[Franklin, J., 2015. How reliable are field-derived biomagnification factors and trophic magnification factors as
indicators of bioaccumulation potential? Conclusions from a case study on per- and polyfluoroalkyl substances.
Available at: https://setac.onlinelibrary.wiley.com/doi/full/10.1002/ieam.1642.]

 

Calculate the BMF if a 120 kg shark consumes 1000 mackerel in one year. Each mackerel weighs 1 kg on average. The Xmackerel=0.3 μg X per kg body weight. Assume chemical X remains in the shark’s body for two years.

[2]

Markscheme

«0.3 μg×2000=»600«μg X» ✔

«600 μg120 kg0.3 μg kg-1=»17 ✔


Award [2] for correct final answer.

M2 may also be correctly expressed to 1 SF.

Examiners report

Many candidates produced the correct answer for M1 but not as many fully scored. Students did not appear to understand the concept, and many missed the idea of 2 years in the calculation. Students should always clearly show their calculations so examiners can award marks throughout the question and potentially award ECF if possible. It is very difficult to do this when students do not show work clearly.

Syllabus sections