Arrange the following complexes in increasing order of conductivity of their solution:

(A) $[Co(NH_3)_3Cl_3]$
(B) $[Co(NH_3)_4Cl_2]Cl$
(C) $[Co(NH_3)_6]Cl_3$
(D) $[Co(NH_3)_5Cl]Cl_2$

Choose the correct answer from the options given below:

(A), (B), (D), (C)

The correct answer is Option (1) → (A), (B), (D), (C)

Conductivity of a solution increases with the number of ions produced on dissociation.

• (A) [Co(NH₃)₃Cl₃]
  → Neutral complex, no ionisation
  → Least conductivity
• (B) [Co(NH₃)₄Cl₂]Cl
  → Dissociates into:
  $[Co(NH₃)₄Cl₂]^+ + Cl^-$ → 2 ions
• (D) [Co(NH₃)₅Cl]Cl₂
  → Dissociates into:
  $[Co(NH₃)₅Cl]^{2+} + 2Cl^-$ → 3 ions
• (C) [Co(NH₃)₆]Cl₃
  → Dissociates into:
  $[Co(NH₃)₆]^{3+} + 3Cl^-$ → 4 ions
  → Highest conductivity

Increasing order of conductivity: $(A) < (B) < (D) < (C)$

Hence, the correct option is (A), (B), (D), (C)