A blue, water soluble compound has no observable reaction with AgNO_3 or BaCl_2.

Question

A blue, water soluble compound has no observable reaction with AgNO_3 or BaCl_2. It reacts with hoi H_2SO_4 to produce a brown gas. The addition of thicket made to an acidic solution of this compound results in the precipitation of a solid that forms u deep blue solution when added to aqueous NH_3. Identify the chemical formula for this compound Action Anion Salt A salt dissolves in water to form a green solution. A precipitate is formed when the aqueous solution is treated with the buffer NH_4Cl/NH_3 and thin acetified. When AgNO_3 is added lo a solution of the salt that is acidified with HNO_3, a while precipitate forms. I his sail reacts with concentrated H_2SO_4 to produce 0 colorless gas. What is the chemical formula for this salt? action Anion Salt A water soluble salt forms a precipitant during the Group 3 analysis. An acidic solution of this precipitant and NaBiO_3 yields a pinkish color This same salt has no reaction to BaCl_2 When mixed with chlorine water and hexane, the hexane layer will turn from colorless to amber. What is the chemical formula for this salt? action Anion Salt A while colored salt contains a caption from Group 4 A flame test performed on this suit shows a green/white flame. It has no reaction with concentrated H_2SO_4 or AgNO_3 It produces an insoluble product with acidic BaCl_2. This salt is not water soluble. What is the chemical formula for this salt? action Anion Salt

Explanation / Answer

6. The compound showed no reaction with AgNO3 and BaCl2 So it is not a sulfate or a chloride salt.

Reaction with H2SO4 gave a brown gas. The gas must be NO2. So, we can conclude that the anion is nitrate, NO3-

Thioacetamide gives H2S in solution. So when the compound produced a dark precipitate with thioacetamide, it must be either Pb, Bi or Cu sulfide precipitated out with thioacetamide. The precipitate produced a blue solution when aqueous ammonia is added confirming the presence of Cu2+.

Cu2+ (aq) + H2S (aq) -----> CuS (s) + 2 H+ (aq)

CuS (s) + NH3 (aq) ------> Cu(NH3)42- (aq) blue colored complex)

CATION: Cu2+    ANION: NO3-   SALT: Cu(NO3)2

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7. Solution of the salt is green colored.

On reaction with basic thioacetamide, the salt produced a precipitate. So the cation may be Al3+, Cr3+, Fe3+, Zn2+, Ni2+, Co2+, Mn2+

A basic H2S solution also has hydroxide ions, which is sufficient to precipitate insoluble hydroxides of aluminum and chromium (III) ions.

Cation can be either Ni2+ or Cr3+ as the salts of both ions are green in solution form.

Anion must be Cl- as a precipitate is formed with acidic AgNO3 and a gasolorless gas Cl2 is produced on reaction with H2SO4

Cl- (aq) + AgNO3 (aq) in acidic solution ----------> AgCl (s) + NO3- (aq)

CATION: Cr3+ / Ni2+    ANION: Cl-   SALT: CrCl3 or NiCl2

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8. Group 3 cations are Zn2+, Fe2+, Fe3+, Ni2+, Cr3+, Al3+, Mn2+

Addition of NaBiO3 in acidic medium results in the solution turning purple, so this confirms the presence of Mn.

2Mn+2 + 5BiO3- + 14H+ ----> 2MnO4- + 5Bi +3 + 7H2O

Chlorine water and hexane is used for detecting the presence of halides.

Cl2 is colorless, Br2 is yellow-orange, and I2 is purple in hexane.

Given that hexane turned amber colored so, the anion must have been Br-

Cl2 (aq) + Br- (aq) ------> Br2 + Cl- (aq)

CATION: Mn2+    ANION: Br-   SALT: MnBr2

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