9. A tablet, with a mass of 1.545 g, is analyzed for the amount of zinc it conta

Question

9. A tablet, with a mass of 1.545 g, is analyzed for the amount of zinc it contains. The tablet is dissolved in water to make 2.00 L of solution. 3.00 mL of this solution is added to reagents and water to give 100.0 mL of a sample that is found to be 2.24 ppm in zinc. What is the tablet? percentage of zinc in the tablet, and how many mg of zinc are in the whole 10. An enologist has prepared 1000. Liters of zinfandel wine. Unfortunately some of the sulfur sprayed on the grapes to prevent insect damage has gotten into the solution and has been reduced to the sulfide ion, giving the wine a slight fragrance of rotten eggs. The wine is analyzed and found to be 436 ppm in sulfide ion. What mass of copper (I) chloride should be added to the wine to precipitate all of the sulfide and leave no copper ion residue (which is toxic): Cu, St. CuS

Explanation / Answer

1)

100 mL solution#2 x (1 L / 1000 mL) x (2.24g Zn / 1000 L solution#2) = 2.24x10^-4g Zn

That is the amount of Zn in solution#2 which is based on 3 mL of solution #1

So you started with this...
2000 mL solution#1 x (2.24x10^-4g Zn / 3 mL solution#1) = 0.150g Zn in the tablet = 150 mg Zn

and % is therefore this...
0.150g Zn / 1.545g x 100% = 9.70%

2)

ppm.. assuming ppm means 436g / 1000 L...

and from the reaction, 1 mole Cu reacts with 1 mole S...
and 1 mole CuCl2 contains 1 mole Cu
and CuCl2 has molar mass = 103.0g/mole

therefore...
1000 L wine x (436g S / 1000 L wine) x (1 mole S / 32.065g S) x (1 mole Cu / 1 mole S) x (1 mole CuCl2 / 1 mole Cu) x (103.0g CuCl2 / 1mole CuCl2) = 1.4 kg CuCl2

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