12-13 - X = 0.90 = moles solvent / (moles solute particles...

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13. How many grams of NaCl must be dissolved in 3.24 L of water at 100. ˚C at sea level to lower the vapor pressure of the water by 76.0 mmHg? a. 585 g b. 324 g c. 19.0 kg d. 1.17 kg e. 11.0 kg f. none of these Key: Vapor pressure of solvent above solution = (mole fraction of solvent) x (vapor pressure of pure solvent 684 torr = X (760 torr)
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Unformatted text preview: X = 0.90 = moles solvent / (moles solute particles + moles solvent) moles solvent = 3,240 g water x 1 mol water/18 g = 180 mol water Remember that when NaCl dissolves, it produces 2 ions (particles) 0.90 = 180 mol water / (moles ions + 180 mol water) moles ions = 20 moles NaCl = 10 g NaCl = 10 moles (58.5 g/mol) = 585 g...
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