Chemistry Transition Elements SET 2019
PMDC Verified Question 47 of 68
What are the coordination number of Fe and Cu in the following compounds \( K_{4}[Fe(CN)_{6}] \), \( [Cu(NH_{3})_{4}]SO_{4} \) respectively
A
-6, -4
B
-6, +4
C
+6,-4
D
+6, +4
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: +6, +4
Concept:

Coordination number refers to the total number of coordinate covalent bonds formed between the central metal ion and the ligands. It is a strict physical count and is always a positive integer.

Solution:

  • In \( K_4[Fe(CN)_6] \), the central iron (\(Fe\)) is surrounded by 6 monodentate cyanide (\(CN^-\)) ligands. Thus, its coordination number is 6.


  • In \( [Cu(NH_3)_4]SO_4 \), the central copper (\(Cu\)) is surrounded by 4 monodentate ammine (\(NH_3\)) ligands inside the coordination sphere. Thus, its coordination number is 4.


  • The respective numbers are +6 and +4.


Why other options are incorrect:

  • Coordination numbers represent a physical count of bonds; they cannot be negative numbers. Negative values typically confuse oxidation states with coordination numbers.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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