12 Most VSAQ’s of D and F Block Elements and Coordination Compounds Chapter in Inter 2nd Year Chemistry (TS/AP)

2 Marks

VSAQ-1 : Scandium is a transition element, but zinc is not. Why?

Scandium (Sc) is classified as a transition element because it has an incomplete d-subshell in its electron configuration ([Ar] 3d1 4s2) and exhibits typical transition metal properties, including variable oxidation states. In contrast, zinc (Zn) is not considered a transition element because it has a filled d-subshell in its ground state ([Ar] 3d10 4s2) and lacks the characteristic properties associated with transition metals.

VSAQ-2 : Why Zn(2+) is diamagnetic whereas Mn(2+) is paramagnetic?

Zn2+ (Zinc ion) is diamagnetic because it has a completely filled d-subshell with no unpaired electrons. In contrast, Mn2+ (Manganese ion) is paramagnetic because it has unpaired electrons in its d-orbitals. Diamagnetic substances have all their electrons paired, while paramagnetic substances have unpaired electrons, making them attracted to an external magnetic field.

VSAQ-3 : Give two reactions in which transition metals or their compounds act as catalysts.

Transition metals and their compounds serve as catalysts in various chemical reactions. In the hydrogenation of alkenes, catalysts like palladium (Pd), platinum (Pt), or nickel (Ni) supported on materials such as carbon or alumina facilitate the addition of hydrogen gas (H2) to carbon-carbon double bonds, converting compounds like ethene (C2H4) to ethane (C2H6). In automobile catalytic converters, platinum (Pt) and palladium (Pd) catalysts aid in the oxidation of toxic carbon monoxide (CO) and unburned hydrocarbons (HC) into less harmful carbon dioxide (CO2) and water (H2O). These transition metal catalysts play crucial roles in industrial and environmental applications by enhancing reaction rates while remaining unchanged in the overall chemical transformations.

VSAQ-4 : What is an alloy? Give example.

An alloy is a homogeneous mixture of two or more elements, with at least one being a metal, resulting in improved properties compared to pure metals. For example, brass is an alloy consisting of copper (Cu) and zinc (Zn), known for its corrosion resistance, malleability, and use in applications like musical instruments and plumbing fixtures.

VSAQ-5 : What are coordination compounds? Give two examples.

Coordination compounds are compounds in which a central metal atom or ion is bonded to surrounding molecules or ions called ligands through coordinate bonds. These compounds exhibit unique properties and find applications in various fields. Two examples of coordination compounds are:

  1. [Co(NH3)6]3+ (hexaamminecobalt(III) ion): This complex consists of cobalt (Co3+) bonded to six ammonia (NH3) ligands, and it is known for its violet color.
  2. [Fe(CN)6]3- (hexacyanoferrate(III) ion or ferricyanide ion): This complex features iron (Fe3+) coordinated to six cyanide (CN⁻) ligands and is commonly used as a stable and redox-active compound in analytical chemistry. Coordination compounds play essential roles in various chemical and biological processes due to their distinctive properties and controlled reactivity.

VSAQ-6 : What are interstitial compounds? Give one example.

Interstitial compounds are solid solutions where small atoms or molecules, called interstitial atoms or molecules, occupy spaces within the crystal lattice of a host metal without significantly disrupting its structure. An example is hydrogen in palladium (Pd-H), where hydrogen atoms are interstitially accommodated within the palladium lattice, leading to unique properties like hydrogen storage and reversibility, making it valuable for hydrogen-related applications, including fuel cells.

VSAQ-7 : What is lanthanide contraction?

Lanthanide contraction is the phenomenon in the periodic table where the atomic and ionic radii of elements in the lanthanide series decrease gradually from left to right across the series, despite increasing atomic numbers. This contraction is primarily due to poor shielding by the inner 4f electrons, leading to stronger nuclear attraction on the outermost electrons. Lanthanide contraction has significant implications in the chemistry and properties of lanthanide elements, particularly in their coordination chemistry and interactions with ligands.

VSAQ-8 : What is mischmetal? Give its composition and uses.

Mischmetal (abbreviated as “MM”) is an alloy primarily composed of rare earth elements, including cerium (Ce) and lanthanum (La), with typical compositions of around 50-60% cerium and 25-30% lanthanum. Mischmetal is known for its pyrophoric properties, igniting spontaneously upon scratching or striking, making it valuable for fire-starting devices and pyrotechnics. It is also used in the production of certain alloys, lighter flints, and as a source of rare earth elements for various applications, including catalysis and glass polishing.

VSAQ-9 : What is ligand?

A ligand is a molecule, ion, or atom that forms coordinate bonds with a central metal atom or ion in a coordination complex. Ligands donate one or more pairs of electrons to the central metal, satisfying its valence electron requirements. Coordination compounds with ligands exhibit diverse structures and properties in coordination chemistry.

VSAQ-10 : CuSO4.5H2O is blue in colour where as anhydrous CuSO4 is colourless. Why?

The difference in color between CuSO4·5H2O (copper(II) sulfate pentahydrate) and anhydrous CuSO4 (copper(II) sulfate) is due to the presence or absence of water molecules in their structures. CuSO4·5H2O is blue because it contains water molecules that form complexes with copper ions (Cu2+), leading to the absorption and reflection of specific wavelengths of light in the visible spectrum. Anhydrous CuSO4 is colorless because it lacks water molecules and the associated complex formation, resulting in no specific light absorption and a colorless appearance.

VSAQ-11 : Calculate the magnetic moment of a divalent ion in aqueous solution if its atomic number is 25.

The magnetic moment (μ) of a divalent ion with an atomic number of 25, Mn²⁺, in an aqueous solution can be calculated using its electron configuration, which has 5 unpaired electrons in the 3d orbital. The formula used is μ = √[n(n+2)], resulting in a magnetic moment of approximately 5.92 Bohr magnetons (μB).

VSAQ-12 : Calculate the ‘spin only’ magnetic moment of Fe(aq)^(+2) ion.

The “spin-only” magnetic moment (μs) of the Fe2+ ion in an aqueous solution is calculated based on its electron configuration, which has 5 unpaired electrons in the 3d orbital. The formula used is μs = √[n(n+2)] BM (Bohr magnetons), resulting in a magnetic moment of approximately 5.92 BM.