Given solutions of (i) Al2(SO4)3; (ii) BaCl2; (iii) Na2SO4(aq); (iv) equal volumes of (ii) and (iii)........which preparation should exert the MOST osmotic pressure?

1 Answer
Jun 2, 2017

We gots (i) Al2(SO4)3; (ii) BaCl2; (iii) Na2SO4(aq); (iv) equal volumes of (ii) and (iii)........I suspect it is solution (iv)

Explanation:

And (iv) a solution obtained by mixing equal volumes of (ii) and (iii).

Now the highest osmotic pressure will be expressed by the solution which CONTAINS LEAST number of ions..........

And (i) has got 5 ions in solution, 2×Al3+, and 3×SO24.................

And (ii) has got 3 ions in solution, 2×Cl, and Ba2+.................

And (iii) has got 3 ions in solution, 2×Na+, and SO24.................

But (iv) mixes (ii) and (iii), and you know, or should know that BaSO4 is pretty insoluble stuff. (All sulfates are soluble except for HgSO4, and CaSO4, and BaSO4.

And thus, the following reaction occurs........

Ba2++SO24BaSO4(s)

In this solution, there remain 2 equiv each of Na+ and Cl. As far as I can tell (and you have not set out the problem as clearly as I would like), because BaSO4 precipitates, this solution, (iv), has the LEAST number of ions in solution, and thus the highest osmotic pressure.