AssignmentEightKey - Take-Home Assignment#8 1 One method for determining the amount of magnesium hydroxide in Milk of Magnesia(MOM is to dissolve a

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Take-Home Assignment #8 1. One method for determining the amount of magnesium hydroxide in Milk of Magnesia (MOM) is to dissolve a portion in a solution of HCl. The resulting Mg 2+ is then precipitated as MgNH 4 PO 4 . After filtering, the precipitate is heated, converting it to a final form of Mg 2 P 2 O 7 . The mass of Mg 2 P 2 O 7 in mg, therefore, is the analytical signal. When a 2.00-mL portion of a sample containing 400.0 mg Mg(OH) 2 per 5.00 mL is treated in this manner, 305.3 mg of Mg 2 P 2 O 7 are obtained. What is the value of k Mg for this analysis? Treat all concentrations in ppm. The analytical equation is mL 5.00 mL 2.00 Mg(OH) mg 400 k O P Mg mg 305.3 2 Mg 7 2 2 × × = Solving for k Mg gives its value as 1.908 with units of mg Mg 2 P 2 O 7 /mg Mg(OH) 2 . 2. A potential interferent in this analysis is Zn 2+ , which will precipitate as ZnNH 4 PO 4 and be isolated as Zn 2 P 2 O 7 . In a separate analysis, a 2.00-mL sample containing 400.0 mg Mg(OH) 2 and 100.0 mg Zn(OH) 2 per 5.00 mL yields a precipitate of 366.6
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This note was uploaded on 04/02/2012 for the course CHEMISTRY 222 taught by Professor Mcdonald during the Fall '11 term at University of Illinois, Urbana Champaign.

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AssignmentEightKey - Take-Home Assignment#8 1 One method for determining the amount of magnesium hydroxide in Milk of Magnesia(MOM is to dissolve a

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