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:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A), (B), (D), (C)
The conductivity of a solution of a complex depends on the number of ions it gives. Ligands inside the square brackets stay bonded to the metal; only the counter ions outside the brackets are set free. Cobalt here is Co(III) with coordination number 6 in every complex, and the more chlorides lie outside the sphere, the more ions and the higher the conductivity.
(A) \( \ce{[Co(NH3)3Cl3]} \): no counter ion; a non-electrolyte, 0 ions.
(B) \( \ce{[Co(NH3)4Cl2]Cl -> [Co(NH3)4Cl2]+ + Cl-} \): 2 ions.
(D) \( \ce{[Co(NH3)5Cl]Cl2 -> [Co(NH3)5Cl]^2+ + 2Cl-} \): 3 ions.
(C) \( \ce{[Co(NH3)6]Cl3 -> [Co(NH3)6]^3+ + 3Cl-} \): 4 ions.
Shortcut: The non-electrolyte (A) conducts least and (C), with three free chlorides, most; only Option (1) starts with (A) and ends with (C).