Question

Which of the following complex has the lowest molar conductivity?

• A. Dichlorotetrammineplatinum(IV) chloride
• B. Dichlorotetramminecobalt(III) chloride
• C. Potassium hexacyanidoferrate(II)
• D. Hexaaquochromium(III) chloride
• E. Pentacarbonyliron(0) has the lowest molar conductivity

Hint:

Compounds with ligands only inside the coordination brackets and no external ions (like $Cl, K, NO_3$ outside) are neutral and do not conduct electricity.

Answer 1

Answer: (E)

Step 1: Understanding the Concept:
Molar conductivity depends on the number of ions produced when the complex dissolves in a solvent. Neutral (non-electrolyte) complexes do not dissociate into ions and thus have the lowest conductivity.
Step 2: Key Formula or Approach:
Identify the number of ions for each complex:
(A) \([Pt(NH_3)_4Cl_2]Cl_2 \rightarrow 3 \text{ ions} \).
(B) \([Co(NH_3)_4Cl_2]Cl \rightarrow 2 \text{ ions} \).
(E) \([Fe(CO)_5] \rightarrow 0 \text{ ions} \).
Step 3: Detailed Explanation:
Pentacarbonyliron(0), \( [Fe(CO)_5] \), is a neutral coordination compound. Since there are no ionizable species outside the coordination sphere, it does not produce any ions in solution. Consequently, its molar conductivity is practically zero, which is the lowest among the given options.
Step 4: Final Answer:
Pentacarbonyliron(0) has the lowest molar conductivity.