Answers_to_Resource_Sheet-2[1] - 1 1 30 1 1 30 = d Cd g d...

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CHEM/ENVS 380 Resource Sheet-2 Solutions Example-1: Assume that the concentration of cadmium in a given tap water is 2 ppb, and that its average concentration in various Cd-containing foods (such as rice, potatoes, green leafy vegetables, offal) is 30 ppb. If a person ingests 2 L of tap water and 1 kg of Cd-containing foods daily, how much of the metal does this person ingest daily? What fraction is coming from foods as opposed to water? First, convert Cd concentration in water from ppb to something explicit. Since the volume of water being ingested is given in liters, the best choice is to use L as the denominator: water L Cd g Cd ppb water in conc Cd 1 2 2 . µ = = Now calculate the total amount of Cd ingested: Daily Cd intake from water = 1 1 4 2 1 2 = × d Cd g d water L water L Cd g Take the same steps with solid food. This time, the amount of food ingested is given in kg, so let’s select kg as the denominator: food kg Cd g Cd ppb food in conc Cd 1 30 30 . = = Daily Cd intake from food =
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Unformatted text preview: 1 1 30 1 1 30 = d Cd g d food kg food kg Cd g Final answer: Total Cd intake is 34 g Cd d-; 88 % from food. Example-2: The acceptable daily intake of a toxin Tox is 10 g per day for an adult weighing 60 kg. If the concentration of Tox in striped bass is 0.2 ppm, how much of this fish can an adult weighing 60 kg eat daily without exceeding this limit? First, re-express the concentration of Tox in the fish using explicit units. Guessing that the amount of fish ingested by a person per day is on the order of grams, we will select g as the denominator: Conc of Tox in fish = 0.2 ppm = fish g Tox g 1 2 . Now find out how many grams of fish will contain a total of 10 g of Tox: fish g Tox g fish g x Tox g 1 2 . 10 = Rearrange the above and solve for x give the final answer: x = 50 g Komada 1/26/2010...
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