Question

The oxidation state of Cr in \([Cr(H_2O)_6]Cl_3\), \([Cr(C_6H_6)_2]\), \(K_2[Cr(CN)_2(O)_2(O_2)(NH_3)]\) respectively are:

• A. \(+3, +4, +6\)
  % option (B) \(+3, +2, +4\)
• B. \(+3, 0, +6\)
• C. \(+3, 0, +4\)
• D. \(+3, 6, +8\)

Hint:

Always separate neutral and charged ligands before calculating oxidation state.

Answer 1

The Correct Option is C

Concept:
•Neutral ligands: \(H_2O, NH_3, C_6H_6\) → charge = 0
•Anionic ligands: \(CN^- = -1\), \(O^{2-} = -2\), \(O_2^{2-} = -2\)

Step 1: \([Cr(H_2O)_6]Cl_3\)
•Complex ion = \([Cr(H_2O)_6]^{3+}\)
•\(H_2O\) is neutral \[ \Rightarrow Cr = +3 \]

Step 2: \([Cr(C_6H_6)_2]\)
•\(C_6H_6\) is neutral ligand
•Overall molecule is neutral \[ \Rightarrow Cr = 0 \]

Step 3: \(K_2[Cr(CN)_2(O)_2(O_2)(NH_3)]\) Let oxidation state = \(x\) \[ x + 2(-1) + 2(-2) + (-2) + 0 = -2 \] \[ x -2 -4 -2 = -2 \Rightarrow x -8 = -2 \Rightarrow x = +6 \] Final: \[ (+3,\ 0,\ +6) \]