You are given an unknown solid or solution and told that it

You are given an unknown (solid or solution) and told that it can be one of the other of the compounds in the pairs listed below. Describe a simple chemical test (Not a flame test) using only reagents from our chemistry kits that would enable you to distinguish between the two possiblities. Describe what you would expect for each and write balanced, net iontic equations for any reaction that occur. Note that this question reviews all of the Qualitative Analysis experiments we have done.

A. AgCl (s) and BaSO4(s)

B. Fe^2+(aq) and Sr^2+(aq)

C. Hg2^2+(aq) and Mn^2+(aq)

D. CoS(s) and BaCO3(s)

Solution

1)

Ag2SO4 (s) --> 2 Ag+ (aq) + SO4^2- (aq), Ksp = 1.4 X 10^-5, which is 8.3 g Ag2SO4/liter of water.

BaSO4 (s) --> Ba^2+ (aq) + SO4^2- (aq), Ksp = 1.1 X 10^-10, which is 0.0022 g BaSO4/liter of water.

So as stated, BaSO4 is more insoluble than Ag2SO4. The products being Ag2SO4 and BaCl2 does not make any sense, since your source has to be AgCl, Ksp = 1.8 X 10^-10, which is 0.0018 g AgCl/liter of water.

So the reaction BaSO4 (s) +2 AgCl (s) --> Ag2SO4 (s) + BaCl2 (aq), the equilibrium position is on the reactant side.

So in a nutshell, it cannot be done. Now if the reaction is Ag2SO4 (s) + BaCl2 (aq) ---> 2 AgCl (s) + BaSO4 (s), it can happen, the solubility of Ag2SO4 is higher than BaSO4 and that of BaCl2 (aq) is also higher than AgCl (s), so that reaction has the equilibrium position on the product side.