Question

A) 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 10.830 g. A 2.402 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 0.264 g of Zn2P2O7 (molar mass = 304.76 g/mol). What is the mass percent of ZnSO4·7H2O in each tablet?

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

Answer 1

ZnSO4·7H2O

n = 10 tablets

mass = 10.83

m = 2.402 g smaple

mol of Zn2P2O7 = mass/MW = 0.264 / 304.76 = 0.000866 mol of Zn2P2O7  

mol of Zn = 2*Zn2P2O7 = 2*0.000866 = 0.001732 mol of Zn

1 mol of Zn = 1 mol of ZnSO4·7H2O

0.001732 mol of Zn = 0.001732 mol of  ZnSO4·7H2O

mass of ZnSO4·7H2O = mol*MW = 0.001732 *287.58 = 0.498 g of ZnSO4·7H2O

this is in m = 2.402 g

% mass of  ZnSO4·7H2O/ tableet = 0.498 /2.402 * 100 = 20.732%

b)

average mass in each

mass of tablet --> 10.83/10 = 1.083 g per tablet

mass of active = 20.732/100*1.083 = 0.2245 g of active ingredient

mass of inacctive = 1.083 -0.2245 = 0.8585 g of inactive ingredient