Question

The oxidation states of Cr in [Cr(H₂O)₆]Cl₃, [Cr(C₆H₆)₂], and K₂[Cr(CN)₂(O)₂(O₂)(NH₃)] respectively are :
(1) +3, +2, and +4
(2) +3, 0, and +6
(3) +3, 0, and +4
(4) +3, +4, and +6

Answer 1

Ans. (2)

(i) [Cr(H₂O)₆]Cl₃ : Hexaaquachromium(III) chloride
x + 6 × 0 + (–1) × 3 = 0
x = +3

(ii) [Cr(C₆H₆)₂] : bis(η⁶–benzene)chromium(0)
y + 2 × 0 = 0
y = 0
(iii) K₂[Cr(CN)₂ (O)₂ (O₂) (NH₃)] :
Potassium amminedicyanidodioxidoperoxidochromate(VI)
2 × 1 + z + 2 × (–1) + 2 × (–2) + (–2) + 0 = 0
z = +6
The oxidation states of Cr in [Cr(H₂O)₆]Cl₃, [Cr(C₆H₆)₂], and K₂[Cr(CN)₂ (O)₂ (O₂) (NH₃)] respectively are +3, 0 and +6.

Answer 2

[Cr(H2O)6]Cl3
x + 6(0) + 3(–1) = 0
x = +3
[Cr(C6H6)2]
x = 2(0) = 0
x = 0
K2[Cr(CN)2(O)2(O2)(NH3)]
2 + x + 2(–1) + 2(–2) + (–2) + (0) = 0
x = +6