Yellow coloured Werner’s cobalt complex gives 3 moles of white coloured AgCl precipitate with AgNO₃ solution.

 The formula of the complex is 

• A

  ${\text{CoCl}}_{\text{3}}.3{\text{NH}}_{\text{3}}$

• B

  ${\text{CoCl}}_{\text{3}}{\text{\hspace{0.17em}.\hspace{0.17em}5NH}}_{\text{3}}$

• C

  ${\text{CoCl}}_{\text{3}}.4{\text{NH}}_3$

• D

  ${\text{CoCl}}_{\text{3}}{\text{\hspace{0.17em}.\hspace{0.17em}6NH}}_{\text{3}}$