Question

Cobalt (III) chloride forms several octahedral complexes with amonia. Which of the following will not give test for chloride ions with silver nitrate at `25^@C`?
A. `CoCl_(3)cdot3NH_(3)`
B. `CoCl_(3)cdot4NH_(3)`
C. `CoCl_(3)cdot5NH_(3)`
D. `CoCl_(3)cdot6NH_(3)`

Answer 1

Correct Answer - A
`[Co(NH_(3))_(6)]Cl_(3)to[Co(NH_(3))_(6)]^(3+)+3Cl^(-)`
`[Co(NH_(3))_(3)]Cl_(3)to[Co(NH_(3))_(3)Cl_(3)]`
`[Co(NH_(3))_(4)Cl_(2)]Clto[Co(NH_(3))_(4)Cl_(2)]^(+)+Cl^(-)`
`[Co(NH_(3))_(5)Cl]Cl_(2)to[Co(NH_(3))_(5)Cl]^(2+)+2Cl^(-)`
So, `[Co(NH_(3)_(3)Cl_(3)]` does not ionise so does not give test for chloride ions