Al2(SO4) 3 solution of 1 molal concentration is present is 1 litre solution of 2.684 gm/ cc. How many moles of BaSO4 would be precipitated on adding BaCl2 in excess.

Dear Student,

The density of the solution is 2.684 g/cc, which includes both the solute Al2(SO4)3 and the solvent water. So, deducing the density of water which is ~ 1 g/cc, we will have 1.684 g/cc of ‚ÄčAl2(SO4)3 .

So, in a litre of solution we have 1.684 x 1000 = 1684 g of Al2(SO4)3 .

Moles of Al2(SO4)3 = 
1684 g342  g mol-1=4.92 mol         [Molar mass of Al2(SO4)3 =342 g mol-1]

Chemical reaction:    Al2(SO4)3 + 3BaCl2   3BaSO4  + 2 AlCl3

For 1 mol of Al2(SO4)3 we will have 3 mol of BaSO4, therefore, for 4.92 mol of Al2(SO4)3 it will produce 3 x 4.92 = 14.76 mol of BaSO4.

Best Wishes !

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