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# Composition of mixture

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1) The Zinc in a 1.200g sample of foot powder was precipitated as ZnNH4PO4. The strong heating of the precipitate yielded 0.4089g of Zn2P2O7. Calculate the mass percent of zinc in the sample of foot powder.

2. A mixture contains only sodium chloride and potassium chloride. A 0.1586g sample mixture was dissolved in water. It took 22.90mL of 0.100 M Silver I nitrate to completely precipitate all of the chloride present. What is the composition (by mass) of the mixture?

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1) the mass percent of zinc in the sample of foot powder 2) composition (by mass) of the mixture of sodium chloride and potassium chloride

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The Zinc in a 1.200g sample of foot powder was precipitated as ZnNH4PO4. The strong heating of the precipitate yielded 0.4089g of Zn2P2O7. Calculate the mass percent of zinc in the sample of foot powder.

Atomic weights

Zinc Zn 65.38
Phosphorus P 30.97376
Oxygen O 15.9994

Molecular weight of Zn2P2O7= 304.70332 =2*65.38+2*30.97376+7*15.9994

304.70332 g of Zn2P2O7 contains 2*65.38=130.76 g of Zinc
Therefore 0.4089 g of Zn2P2O7 contains 0.17547 (=0.4089*130.76/304.70332) g of Zinc

Thus 1.200 g sample of foot powder contains 0.17547 g of Zinc

Mass percent of Zinc= 14.62% =(0.17547/1.2)

2. A mixture contains only sodium chloride and potassium chloride. A 0.1586g sample mixture was dissolved in water. It took 22.90mL of 0.100 M ...

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