# Cobalt (III) chloride forms several octahedral complexes with ammonia. Which of the following will not give test of chloride ions with silver nitrate at $25^{\circ}C$? Option 1) $CoCl_{3}\cdot 4NH_{3}$ Option 2) $CoCl_{3}\cdot 5NH_{3}$ Option 3) $CoCl_{3}\cdot 6NH_{3}$ Option 4) $CoCl_{3}\cdot 3NH_{3}$

As learned in concept no

Coordination Sphere -

The central atom/ion and the ligands attached to metal are enclosed in square bracket and this collectively termed as coordination sphere

- wherein

eg:

$K_{4}\left [ Fe\left ( CN \right )_{6} \right ]$

$K^{+} \rightarrow$ Counter ion

$\left [ Fe\left ( CN \right )_{6} \right ]^{4-} \rightarrow$  Coordination sphere

The co-ordination number of Cobalt (III) in octahedral complex is 6. In $CoCl_{3}.3NH_{3}$, all we have is 6 ligands, which implies all of them are in the co-ordination sphere and won't ionize.

$\therefore$ There will be no precipation of Ages and no test will be positive

Option 1)

$CoCl_{3}\cdot 4NH_{3}$

This is incorrect option

Option 2)

$CoCl_{3}\cdot 5NH_{3}$

This is incorrect option

Option 3)

$CoCl_{3}\cdot 6NH_{3}$

This is incorrect option

Option 4)

$CoCl_{3}\cdot 3NH_{3}$

This is correct option

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