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Living By Chemistry SECOND EDITION

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Presentation on theme: "Living By Chemistry SECOND EDITION"— Presentation transcript:

1 Living By Chemistry SECOND EDITION
Unit 4: TOXINS Stoichiometry, Solution Chemistry, and Acids and Bases

2 Lesson 74: Lethal Dose Toxicity

3 ChemCatalyst Which substance do you think is most toxic to you—alcohol (ethanol, C2H6O), aspirin (salicylic acid, C7H6O3), or arsenic (III) oxide (As2O3)? Explain your thinking.

4 Key Question How much is too much of a substance?

5 You will be able to: calculate the toxic dose for a variety of substances, given the LD50 explain the role of dosage in toxicity

6 Prepare for the Classwork
You will work individually or in pairs. Lethal dose (LD50): the amount of an ingested substance that kills 50% of a test sample of animals. It is expressed in mg/kg, or milligrams of substance per kilogram of body weight.

7 Discussion Notes Toxicity depends on two quantities: amount of toxic substance and mass of the organism. All substances are toxic in large enough doses, even sugar and water.

8 Discussion Notes (cont.)
The smaller the lethal dose, or LD50, the more potentially dangerous a substance is. Many toxic substances can be therapeutic at lower doses.

9 Wrap Up How much is too much of a substance?
Toxicity is relative to dosage: The toxicity (or therapeutic effect) of a substance depends on the dose in which it is received. The lethal dose (or therapeutic dose) of a substance is often expressed as a ratio between a certain mass of the substance and 1 kilogram of the body mass of an organism exposed to the substance.

10 Check-In Methadone is a medication used as a painkiller and as a treatment for those recovering from heroin addiction. The LD50 for methadone is 95 mg/kg. a. Would you consider methadone to be more or less toxic than acetaminophen (LD50 = 2404 mg/kg)? than aspirin (LD50 = 200mg/kg)? b. Explain how you would calculate the amount of this substance that would be lethal to a 120 lb human.


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