Chemistry Test 278

The correct answer is option B.

The I.U.P.A.C. name for Fe(C₅H₅)₂ is bis(η⁵ -cyclopentadienyl) iron(II) 

The oxidation state of iron is +2 and is written in parenthesis in roman numerals. Two cyclopentadienyl ligands are coordinated to Fe. The prefix bis indicates 2. η⁵ indicates that the cyclopentadienyl ligands are penta coordinates.

Since both cation & anion constitute coordination sphere so it exhibit coordination isomerism and contains ambident ligand so, it shows linkage isomerism

A complex compound in which the oxidation number of metal is zero is [Ni(CO)_4​]. In this complex, the oxidation number of both metal and ligand is zero.

The oxidation number of metal in the complexes K₄​[Fe(CN)₆​], K₃​[Fe(CN)₆​] and [Pt(NH₃)₄]Cl₂ are +2, +3 and +2 respectively.

O. N. of Al = +3

O. N. of B = + 3

[BF₄]^-

[Al(C₂O₃)₃]^3-

The correct answer is B: CNS⁻.

Explanation:

• Linkage isomerism occurs when a ligand can coordinate to the central metal ion through two different atoms, leading to different isomers.

• Flexidentate ligands are ligands that can form multiple bonds to the metal centre via different donor atoms.

CNS⁻ (Thiocyanate) is an example of a ligand that can exhibit linkage isomerism. The thiocyanate ion (CNS⁻) can bind to the metal through the nitrogen atom (N) or the sulfur atom (S), leading to two different isomers:

1. N-bonded thiocyanate (also called isothiocyanate),

2. S-bonded thiocyanate.

This makes CNS⁻ a flexidentate ligand, as it can coordinate through two different donor atoms (N or S), showing linkage isomerism.

Thus, the correct answer is B: CNS⁻.

Werner’s coordination theory describes primary and secondary valencies in coordination compounds:

• Ligands are connected to the metal ions by covalent bonds: Incorrect. Werner proposed that ligands are bound by coordinate (dative) bonds, not covalent bonds (Statement 1 is false).

• Secondary valencies have directional properties: Correct. Secondary valencies (coordination number) determine the geometry of the complex (e.g., octahedral, tetrahedral), which is directional (Statement 2 is true).

• Secondary valencies are non-ionizable: Correct. Secondary valencies involve ligands bound to the metal within the coordination sphere, which do not ionize in solution (Statement 3 is true).

• Secondary valencies are satisfied by either neutral or negative ligands: Correct. Secondary valencies are satisfied by ligands like NH₃ (neutral) or Cl⁻ (negative) (Statement 4 is true).

Thus, statements 2, 3, and 4 are correct.

Answer: A

Ammonia acts as a very good ligand but ammonium ion does not form complexes because NH₄⁺ ion does not have any lone pair of electrons.

Complexes are formed by the donation of a pair of electrons from ligand to metal. In ammonia, N atom has one lone pair of electrons. So it can form complexes. 

Nitrogen donates this lone pair of electrons to the proton to form an ammonium ion. NH₄⁺ ion does not possess any lone pair of electrons which it can donate to central metal ion therefore it does not form complexes. 

Thus, Ammonia can be a very good ligand but ammonium ion does not form complexes.

Meso tartaric acid is optically inactive because it has a plane of symmetry.

Mohr's salt is a compound known to contain two primary cations, namely the ammonium cation (denoted by NH₄⁺) and the ferrous cation (denoted by Fe²⁺). Therefore, Mohr's salt can be categorized as a double salt of ammonium sulphate and ferrous sulphate. All others are complexes.

The correct answer is D: Ferrous ferrocyanide.

Explanation:

• Turnbull's blue is a type of pigment that is a ferrous ferrocyanide. It is a compound containing iron in the +2 oxidation state (ferrous, Fe²⁺) and ferrocyanide ions (Fe₄[Fe(CN)₆]₃⁻).

• The name "Turnbull's blue" is used to refer to a specific pigment composed of this complex, which is known for its deep blue color.

Thus, the correct answer is D: Ferrous ferrocyanide.