Assume that a given solution caontains Ag+or Ba2+ or a mixture of both. A reasonable method for doing a qualitative analysis on this solution might be sketched out as followes (remember || means a precipitate forms and | means a solution remains. It is alwasys assumed that solution are separated from precipitates before adding the next reagent.)

Question

Diagram: solution containing Ag+ and or/Ba 2+ is underlined and there is a straight line down that then splits into 2. next to the down line it says dilute Nacl on the left wing that down down it does this :|| white ppt, indicated Ag+ and on the right wing it says dilute Na2So4 and then splits into 2 again left side || white ppt indicated Ba2+ and the right side |

a) why is the precipitate formed with Ag+
b) What is the precipitate formed with Ba 2+
c) Explain why a precipitate formed with Ag+ when aqueous NaCl was added, but none formed with Ba2+ ( a chemical reaction and a statemnet about solubility is a sufficeint explaination.)
D)could a solution of HCl be used in the above scheme rather than aqeous NaCl? Explain.
E)Supose you wanted to verify further that Ag+ is a present in a solution. To do this you would have to dissolve the precipitate formed when Nacl was added. What considerations would be important in chossing a reagent to dissolve the pricipitate?
F)It has been observed that the precipitate reffered to in parts a and e above will dissolve in aqueous ammonia. A white precipitate forms when nitric acid is addd to this solution. Using chemical equations, descirbe why the precipitate dissolves and name the precipitate which is obtained when nitric acid is added.Explaion why it forms.

Answer 1

a) Because the Ksp for AgCl is exceeded.
b) Ba^2+ + SO4^2- ==> BaSO4(s)
c) See answers to a and b above. Put that into words.
d) Yes, if dilute HCl were used.
e) identity of the material, its solubility and ease of making solutions, its stability, etc.
f) AgCl + 2NH3 ==> Ag(NH3)2Cl. The AgCl dissolves in NH3 because the complex ion (Ag(NH3)2^2+) is more stable than the AgCl. Ag(NH3)2Cl is silver ammine chloride. When HNO3 is added, that neutralizes the NH3 so it is no longer available and AgCl re-precipitates.

Answer 2

Thanks!