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Coordination Compounds

Question
CBSEENCH12010987
Wired Faculty App

Consider the following reaction and statements:

[Co(NH3)4Br2]+ + Br- →   [Co(NH3)3Br3] + NH3

(I) Two isomers are produced if the reactant complex ion is a cis-isomer
(II) Two isomers are produced if the reactant complex ion is a trans-isomer
(III) Only one isomer is produced if the reactant complex ion is a trans-isomer
(IV) Only one isomer is produced if the reactant complex ion is a cis – isomer

The correct statements are

  • (II) and (IV)

  • (I) and (II)

  • (I) and (III)

  • (III) and (IV)

Solution

C.

(I) and (III)

Question
CBSEENCH12010991
Wired Faculty App

The trans-alkenes are formed by the reduction of alkynes with

  • Sn - HCl

  • H2 – Pd/C, BaSO4

  • NaBH4

  • Na/liq. NH3

Solution

D.

Na/liq. NH3

Na/Liq. NH3 reduces alkynes into trans alkene (trans addition).

Birch reduction is the anti addition. So trans alkene will be produced.

 

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Question
CBSEENCH12010998
Wired Faculty App

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, +2, and +4

  • +3, 0, and +6

  • +3, 0, and +4

  • +3, +4, and +6

Solution

B.

+3, 0, and +6

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

(ii) [Cr(C6H6)2] : bis(h6–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.

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Question
CBSEENCH12011050
Wired Faculty App

Which of the following has longest C-O bond length? (free C-O bond length in CO is 1.128 A0)

  • [Co(CO)4]-

  • [Fe(CO)4]-2

  • [Mn(CO)6]+

  • Ni(CO)4

Solution

B.

[Fe(CO)4]-2

As the negative charge on metal carbonyl complex increases back pi bonding increases and hence the bond length of C-O bond increases while the bond length of metal-carbon bond decreases. Hence,[Fe(CO)4]2- has longest C-O bond length among the given complexes.
The correct order of bond length of the given complexes is
[Mn(CO)6]+<[Ni(CO)4]<[Co(CO)4]-<[Fe(CO)4]2-

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