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AP®Environmental ScienceCollege BoardExam QuestionsUnit 8: Aquatic & Terrestrial PollutionLethal Dose 50%

Lethal Dose 50% (College Board AP® Environmental Science): Exam Questions

6 mins6 questions
11 mark

The LD50 for methyl mercury in rats is 11.9 mg/kg. What concentration of mercury would be needed to reach the LD50 for a 0.75 kg rat?

  • 0.6 mg

  • 5.95 mg

  • 8.9 mg

  • 15.9 mg

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21 mark

Salt is often applied to roads in winter to melt ice. Students are conducting an experiment to determine the median lethal dose (LD50) of sodium chloride (NaCl), magnesium chloride (MgCl2), and potassium chloride (KCl) on the germination of radish seeds.

Which experimental design would be most appropriate?

  • Expose radish seeds to a single high concentration of each salt and record the number of seeds that fail to germinate.

  • Expose radish seeds to a range of concentrations for each salt and determine the concentration at which 50% of the seeds fail to germinate.

  • Expose radish seeds to varying concentrations of a mixture containing equal parts of NaCl, MgCl2, and KCl, and observe overall germination rates.

  • Expose radish seeds to a range of concentrations of one salt, then apply the same concentrations to the other salts without adjusting for their specific properties.

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31 mark

Which of the following claims is best supported by the data from the experiment?

Salt 

LD50

Sodium chloride

3.5 grams

Magnesium chloride 

1.0 grams

Potassium chloride 

2.1 grams 

  • Magnesium chloride is the least toxic of the three salts tested.

  • Radish seeds can survive greater concentrations of sodium chloride than magnesium chloride and potassium chloride exposure.

  • Magnesium chloride was ineffective at melting ice. 

  • Sodium chloride should not be used to salt roads because it has the highest toxicity.

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41 mark

Which herbicide has no threshold level of toxicity?

Graph showing mortality percentage against concentration (mg/kg) with four curves labelled A, B, C, D, indicating different mortality responses.

  • A

  • B

  • C

  • D

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51 mark

All four of the herbicides used can negatively impact human health if they were to enter the drinking water supply. Public health experts have set a maximum application concentration of 2.0 mg/kg. Which of the herbicides would be most effective at that concentration?

Graph showing mortality percentage against concentration in mg/kg. Four curves labelled A to D depict different mortality responses over the range.

  • A

  • B

  • C

  • D

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61 mark

What is the LD 50 of herbicide D?

Graph showing mortality percentage versus concentration (mg/kg) with three S-shaped curves (orange, blue, green) and labels A, B, C, D; linear trend line.

  • 0 mg/kg

  • 2.5 mg/kg

  • 3.5 mg/kg

  • 5 mg/kg

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