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.)
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.
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.
Thanks!
a) The precipitate formed with Ag+ is a white ppt, indicating the presence of silver ions in the solution.
b) The precipitate formed with Ba2+ is also a white ppt.
c) The precipitate formed with Ag+ when aqueous NaCl was added is due to the formation of silver chloride (AgCl), which is insoluble in water. On the other hand, no precipitate forms with Ba2+ because barium chloride (BaCl2) is soluble in water.
d) HCl could be used instead of aqueous NaCl. Both HCl and NaCl contain chloride ions, which can react with silver ions to form the insoluble silver chloride precipitate.
e) When choosing a reagent to dissolve the precipitate, it is important to consider the solubility of the precipitate. In this case, since the precipitate is silver chloride (AgCl), a reagent that can dissolve AgCl, such as dilute ammonia, would be suitable.
f) The precipitate dissolves in aqueous ammonia because ammonia acts as a complexing agent and forms a soluble complex with the silver ions, typically forming a complex called tetraammine silver (II) chloride [Ag(NH3)4]Cl2. When nitric acid is added to the solution, a white precipitate of silver chloride (AgCl) forms again. This occurs because nitric acid reacts with the ammonia to produce nitric oxide (NO), which can react with the silver ions to form AgCl. The precipitate forms because AgCl is insoluble in water.
a) The precipitate formed with Ag+ is a white ppt. This is because when dilute NaCl is added to a solution containing Ag+, a chemical reaction occurs between Ag+ and Cl- ions to form AgCl, which is insoluble in water and appears as a white precipitate.
b) The precipitate formed with Ba2+ is also a white ppt. When dilute Na2SO4 is added to a solution containing Ba2+, a chemical reaction occurs between Ba2+ and SO42- ions to form BaSO4, which is insoluble in water and appears as a white precipitate.
c) The precipitate formed with Ag+ when NaCl was added because AgCl is insoluble in water. On the other hand, no precipitate formed with Ba2+ when Na2SO4 was added because BaSO4 is also insoluble in water. This can be explained based on the solubility rules, which state that most chlorides are soluble in water, while most sulfates are only sparingly soluble in water.
d) A solution of HCl cannot be used in the above scheme instead of aqueous NaCl. This is because HCl will react with Ag+ to form AgCl, which is the desired precipitate used for identifying the presence of Ag+. However, HCl does not react with Ba2+ to form a precipitate, so it would not be suitable for identifying the presence of Ba2+.
e) When choosing a reagent to dissolve the precipitate formed when NaCl was added, it is important to consider that the reagent should be able to react with AgCl to form a soluble complex or compound. Ammonia (NH3) solution is commonly used for this purpose as it forms a soluble complex with AgCl called [Ag(NH3)2]+. Therefore, adding aqueous ammonia can dissolve the AgCl precipitate.
f) The precipitate dissolves in aqueous ammonia because ammonia forms a complex with AgCl. The chemical equation for the reaction is:
AgCl + 2NH3 → [Ag(NH3)2]+ + Cl-
When nitric acid is added to the solution containing the dissolved complex [Ag(NH3)2]+, it reacts with the ammonia to generate H+ ions. The chemical equation for the reaction is:
[Ag(NH3)2]+ + 2H+ → Ag+ + 2NH4+
The white precipitate formed when nitric acid is added is AgCl, which is insoluble in water. This precipitate confirms the presence of Ag+ in the original solution.
a) The precipitate formed with Ag+ is white in color. This is because when a solution containing Ag+ ions is mixed with dilute NaCl, a chemical reaction occurs, resulting in the formation of silver chloride (AgCl) precipitate. The equation for the reaction is:
Ag+(aq) + Cl-(aq) -> AgCl(s)
b) The precipitate formed with Ba2+ is also white in color. When a solution containing Ba2+ ions is mixed with dilute Na2SO4, a chemical reaction occurs, leading to the formation of barium sulfate (BaSO4) precipitate. The equation for the reaction is:
Ba2+(aq) + SO42-(aq) -> BaSO4(s)
c) A precipitate formed with Ag+ when aqueous NaCl was added because AgCl has low solubility in water. On the other hand, no precipitate is formed with Ba2+ because BaSO4 has extremely low solubility in water, so most of it remains as a solid, resulting in a precipitate. This difference in solubility is what causes the formation of precipitates in these cases.
d) A solution of HCl cannot be used in the above scheme instead of aqueous NaCl. This is because HCl can react with Ba2+ ions and form a precipitate of barium chloride (BaCl2). Therefore, if HCl were used instead of NaCl, it would interfere with the analysis and lead to incorrect results.
e) To dissolve the precipitate formed when NaCl was added and verify further that Ag+ is present in the solution, a reagent that can react with silver chloride and form a soluble complex would be needed. Ammonia solution (NH3) is commonly used for this purpose. When the silver chloride precipitate is treated with aqueous ammonia, it forms a soluble complex called tetraamminesilver(I) chloride:
AgCl(s) + 2NH3(aq) -> [Ag(NH3)2]Cl(aq)
Important considerations in choosing a reagent to dissolve the precipitate include its ability to react selectively with the precipitate, forming a soluble product, and not interfering with other ions present in the solution.
f) The precipitate formed with Ag+ (AgCl) dissolves in aqueous ammonia due to the formation of a silver-ammonia complex. The equation for the reaction is:
[Ag(NH3)2]Cl(aq) + NH3(aq) -> [Ag(NH3)2]+(aq) + Cl-(aq)
When nitric acid is added to the solution containing the silver-ammonia complex, a white precipitate of silver chloride (AgCl) is formed again. This is because nitric acid is a strong acid and can react with ammonia, displacing the ammonia ligands from the silver ion, resulting in the regeneration of silver chloride.