The active ingredient in a zinc nutritional supplement is ZnSO4·7H2O (molar mass

Question

The active ingredient in a zinc nutritional supplement is ZnSO4·7H2O (molar mass = 287.58 g/mol). Ten zinc tablets containing a mix of the active ingredient and an inactive filler were ground and mixed together thoroughly. The total mass of these ten tablets was 11.890 g. A 2.242 g sample of the finely ground tablets was dissolved in an acidic solution. The solution was neutralized with ammonia and subsequently warmed in a water bath. Addition of (NH4)3PO4 to the solution resulted in the precipitation of ZnNH4PO4. The precipitate was filtered and dried, then ignited to produce 0.180 g of Zn2P2O7 (molar mass = 304.76 g/mol). What is the mass percent of ZnSO4·7H2O in each tablet?

1-%ZnSO4·7H2O

2- What is the average mass of the active ingredient ZnSO4·7H2O and inactive filler in each tablet?

1-............g ZnSO4·7H2O

2-..........g inactive filler

Explanation / Answer

Moles of Zn2P2O7 = mass of ZnP2O7 / Molar mass ofZn2P2O7 = ( 0.18 /304.76) = 5.906 x 10^ -4

Moles of ZnNH4PO4 = 1/2 moles of Zn2P2O7 = 2.953 x 10^ -4

Now Moles of ZnSO4.7H2O = 2.953 x 10^ -4

mass of ZnSO4.7H2O = moles xmolar mass = 2.953 x 10^ -4 x 287.58 = 0.0849265 g

mass % of it = 100 x mass of ZnSO4.7H2O / sample mass = ( 100 x 0.0849265 /2.242) = 3.788 %

2) since 10 tablets has 11.89g , one tablet mass = 1.189 g

avergae mass of ZnSO4.7H2O in one tablet = 1.189 x 3.788 /100 = 0.045 g

mass of inactive filler = 1.189-0.045 = 1.144 g

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