The tests results showed that unknown # 4 was positive fro Hg2^2+ as well as Fe+

Question

The tests results showed that unknown # 4 was positive fro Hg2^2+ as well as Fe+.

4. In your testing, several precipitates are formed, and then dissolved as complexes. Select threeof these situations for which to write a balanced reaction equation.
5. When Mn2+ ions are separated from the mixture, they go through a series of oxidizing andreducing steps. Write the reaction equations that describe this process.
6. The NH3 solution is used, in three separate instances, to separate two ions. In each of thesecases, one ion forms a precipitate and the other ion remains in solution as a complex.Describe each of these instances, using reaction equations.
7. Al3+ and Zn2+ ions are amphoteric. Describe how the amphoteric nature of these ions isshown in your testing.

Known Unknown Test Procedure results conclusion results conclusion 1 Add HCl to test tube #1 White ppt Ag+,Pb+,Hg2+ White ppt Ag+,Pb+,Hg2+ 2 Add H2SO4 to check for Pb+ White ppt Pb+ No white ppt No Pb+ 3 Add NH3 to check for Hg2^2+ Grey ppt Hg2^2+ Grey ppt Hg2^2+ present 4 Add 15 drops HCl check pH White ppt Ag+ No ppt No Ag+ 5 Add HNO3 and NaBiO3 Purple Mn+ No purple No Mn+ 6 Add KNO2 to check for Co2+ Yellow ppt Co2+ No yellow No Co2+ 7 Add NH3 to check for Cu2+ Blue color Cu2+ No blue No Cu2+ 8 Add KSCN for Fe+ Deep red Fe+ Red color Fe+ present 9 Add HCl, drop to H2O for Bi3+ White cloud Bi3+ No cloud No Bi3+ 10 Add HCl & NH3 for Al3+ Gelatinous Al3+ No Gelatine No Al3+ 11 Add HCl & FeCN for Zn2+ White ppt Zn2+ No ppt No Zn2+

The tests results showed that unknown # 4 was positive fro Hg2^2+ as well as Fe+.

4. In your testing, several precipitates are formed, and then dissolved as complexes. Select threeof these situations for which to write a balanced reaction equation.
5. When Mn2+ ions are separated from the mixture, they go through a series of oxidizing andreducing steps. Write the reaction equations that describe this process.
6. The NH3 solution is used, in three separate instances, to separate two ions. In each of thesecases, one ion forms a precipitate and the other ion remains in solution as a complex.Describe each of these instances, using reaction equations.
7. Al3+ and Zn2+ ions are amphoteric. Describe how the amphoteric nature of these ions isshown in your testing.

Explanation / Answer

4.

Th ppt of aluminium hyoxide is formed when Al+3 is treated wit NaOH

The ppt get dissolved on addng excess of NaOH

Al(OH)3 + NaOH        > Na+ + [Al(OH)4]-

b) Cr3+ ions with NaOH solution

[Cr(H2O)6]3+ + 3OH- ---> [Cr(H2O)3(OH)3] + 3H2O
green solution----------------light green ppt

And in excess:

[Cr(H2O)3(OH)3] + OH- ---> [Cr(H2O)2(OH)4]- + 4H2O
light green ppt--------------dark green solution

c ) siver ppt out as silver chloride

Ag+ +Cl- --> AgCl(S)

AgCl dissolves in ammonia due to the formation of the complex ion [Ag(NH3)2]+),

AgCl + 2NH3 --> [Ag(NH3)2]+

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