Desperately need help (1 Viewer)

[lanvins]

1. The chlorine in a .63g sample of chlorinate pesticide, DDT (C14H9Cl5), is precipitated as silver cloride. What mass of silver chloride is formed?

2.A precipitate of Fe2O3, of mass 1.43g, was obtained by treating a 1.5L sample of bore water. What was the concentration of iron, in molL-1, in the water?

3. A .5g sample of sodium sulfate (Na2SO4) and .5g sample of aluminium sulfate (Al2(SO4)3 ) were dissolved in a volume of water and excess barium chloride added to preciptate barium sulfate. What was the totoal mass of barium sulfate produced?

i keep getting 1.02g for this one but the answer is 1.85g
<ABBR title="2008-03-15 21:58:38">

 

[Undermyskin]

n DDT = 0.63/(12.01*14+1.008*9+35.45*5)= 1.777*10^-3 mol

n Cl-= 1.777*5*10^-3=8.887*10^-3 mol

AgCl : ratio 1:1 --> m AgCl formed= n*(107.9+35.45)= 1.27 g (approx)

2. n Fe2O3= 1.43/(55.9*2+48)= 8.95*10^-3 mol

n Fe3+= 0.0179 mol

[Fe3+]=0.0179/1.5= 0.012 mol/L

3.
n Na2SO4= .5/(22.99*2+32.1+64)=3.52 *10^-3 mol

n Al2(SO4)3 = .5/(54+96.3+192)= 1.461*10^-3 mol ---> n SO4 (2-)= 4.382*10^-3 mol

---> n SO4 (2-)= 7.902*10^-3 mol

m BaSO4= n*(137.3+32.1+64)=1.84g.

 

[lanvins]

thanks man