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Living By Chemistry SECOND EDITION Unit 4: TOXINS Stoichiometry, Solution Chemistry, and Acids and Bases
Lesson 79: How Sweet It Is Comparing Amounts
Chem. Catalyst Consider two cans of carbonated soft drink. One is regular, and the other is diet. a. Which do you think is more toxic, the regular soft drink or the diet soft drink? Explain your reasoning b. What information would help you answer this question?
Key Question How can you use moles to compare toxicity?
You will be able to: • use moles and molar mass to compare the amounts of different substances • discuss the safety of sweeteners
Prepare for the Demonstration Work individually.
Discussion Notes Aspartame molecules are much sweeter than fructose molecules. The safety of artificial sweeteners has been a subject of debate for years.
Discussion Notes (cont. ) It is interesting to compare the LD 50 for fructose and for aspartame. Regular soft drink (fructose) Diet soft drink (aspartame) Lethal dose for a 64 kg person 29, 7000 mg/kg • 64 kg = 1, 900, 000 mg = 1, 900 g 10, 000 mg/kg • 64 kg = 64, 000 mg = 64 g Number of cans 1, 900 g/40 g/can ≈ 48 cans 64 g / 0. 225 g/can ≈ 280 cans
Wrap Up How can you use moles to compare toxicity? • The smaller the LD 50, the more toxic a substance is. However, the LD 50 values are of limited use in determining the long-term effects of a substance.
Check-In Imagine two substances of equal mass with molecules that are equally toxic. Would you rather be exposed to the substance with the larger molar mass or the smaller molar mass? Explain your reasoning.