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Unformatted text preview: 1 CEE 350 Homework #3 Problem 1 (Textbook Problem 2.22, 0.5 points) One-half gram of solid calcium sulfate, CaSO 4 (s) is added to 1 L of pure water. Immediately, the solid begins to dissolve according to the following reaction: l 2 4 2 4 SO Ca CaSO What is the concentration of dissolved sulfate in the water once the equilibrium is achieved? (The solubility product of CaSO 4 K sp is 210-5 ). At the equilibrium, the molar concentration of calcium and sulfate are equal and their product can be determined as &gt; @&gt; @ sp K x SO Ca 2 2 4 2 Accordingly, L mol K x sp / 10 47 . 4 3 The weight concentration of the dissolved calcium sulfate is therefore L g mol g L mol MW x L g C CaSO CaSO / 61 . / 136 / 10 47 . 4 / 3 4 4 u This concentration is above the total mass of calcium sulfate added to the system (0.5 g/L). This is means that the actual concentration of calcium and sulfate will be determined by the amount added rather than by the solubility product. In other words, the concentration of sulfate in the solution will be L g mol g mol g L g MW MW W L g C SO CaSO CaSO SO / 35 . / 136 / 96 / 5 . / 4 4 4 4 u Problem 2 (Textbook Problem 2.25, 0.5 points) Solid aluminum phosphate AlPO 4 is in equilibrium with its ions in solution: l 3 4 3 4 PO Al AlPO with K sp =10-22 . Find the equilibrium concentrations of phosphate ions (in mg/L) in the solution....
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This note was uploaded on 03/31/2012 for the course CEE 350 taught by Professor Korshin during the Spring '10 term at University of Washington.
- Spring '10