12-19

12-19 - where x is the unknown weight of solution Thus x =...

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19. I have 2.0 mol of glucose in a solution of glucose (C 6 H 12 O 6 ) and water. If the solution is 2.0 x 10 3 ppm glucose, how much water does it contain? a. 180 L b. 18 kg c. 1.0 x 10 6 g d. 0.72 g e. 9.0 x 103 mL f. none of these Key: The concentration of the solution is equivalent to 2000 g of glucose in a million g of solution. But the amount of solution in this sample is that quantity which contains 2 mol of glucose (which is the equivalent of 2.0 mol x 180 g/mol = 360 g). The size of this sample can be determined by setting up a proportionality: 2000 g glucose/1,000,000 g solution = (360 g)/ x g of solution
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Unformatted text preview: where x is the unknown weight of solution. Thus x = 180,000 g We assume that the weight of water is so much greater than the weight of glucose in the solution that we can use the weight of the solution as the weight of water, especially given the small number of significant digits being used. This assumption also implies that the density of the solution is approximately that of pure water, meaning that the volume of the solution is 180 L, good to 2 significant digits at least. FUN!...
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