91. Which of the following elements shows the greatest tendency to form complexes?
A) Zn
B) Sc
C) Cu
D) Co
Answer: D
Explanation:
Cobalt (CoCo) shows the greatest tendency to form complexes due to its ability to exist in multiple oxidation states, such as +2 and +3, and its relatively small ionic size, which favors coordination with ligands.
92. Which of the following is not a transition metal?
A) Chromium
B) Manganese
C) Zinc
D) Iron
Answer: C
Explanation:
Zinc is not considered a transition metal because it does not have an incomplete d-orbital in its most common oxidation state (Zn2+), where the electron configuration is [Ar]3d10. Transition metals, by definition, must have partially filled d-orbitals.
93. The electronic configuration of Cr3+ is:
A) [Ar]3d5
B) [Ar]3d3
C) [Ar]3d4
D) [Ar]3d2
Answer: B
Explanation:
The electronic configuration of Cr3+ (chromium in the +3 oxidation state) is [Ar]3d3. This configuration arises from the removal of three electrons from the 3d54s13d54s1 configuration of neutral chromium.
94. Which of the following compounds is used as a chromophore in dyes and pigments?
A) FeSO4
B) Cr2O3
C) MnO2
D) Co(NO3)2
Answer: B
Explanation:
Cr2O3 (chromium(III) oxide) is used as a chromophore in dyes and pigments. It is responsible for the green color in many materials and is commonly used in paints and coatings.
95. Which of the following is not a property of lanthanides?
A) They form colored ions
B) They have high ionization energies
C) They show +3 oxidation state predominantly
D) They exhibit paramagnetism
Answer: B
Explanation:
Lanthanides do not have high ionization energies; in fact, their ionization energies are relatively low compared to other elements. This is why they readily lose three electrons to form Ln3+ ions, their most common oxidation state.
96. Which of the following transition metals is used in the catalytic converter of automobiles to reduce emissions?
A) Copper
B) Platinum
C) Iron
D) Nickel
Answer: B
Explanation:
Platinum is used in the catalytic converters of automobiles to reduce harmful emissions. It helps in the oxidation of carbon monoxide and hydrocarbons and the reduction of nitrogen oxides into less harmful substances.
97. The coordination number of cobalt in [Co(NH3)6]3+ is:
A) 4
B) 5
C) 6
D) 7
Answer: C
Explanation:
The coordination number of cobalt in [Co(NH3)6]3+ is 6, as there are six ammonia ligands attached to the central cobalt ion. This results in an octahedral geometry around the cobalt ion.
98. Which of the following compounds exhibits linkage isomerism?
A) [Co(NH3)6]Cl3
B) [PtCl2(NH3)2]
C) [Co(NO2)(NH3)5]2+
D) [Cr(H2O)6]Cl3
Answer: C
Explanation:
[Co(NO2)(NH3)5]2+ exhibits linkage isomerism. The NO2− ligand can bind to the metal ion through either the nitrogen atom (nitro) or the oxygen atom (nitrito), giving rise to isomers.
99. Which one of the following elements does not belong to the actinide series?
A) Uranium
B) Thorium
C) Ytterbium
D) Neptunium
Answer: C
Explanation:
Ytterbium belongs to the lanthanide series, not the actinide series. Actinides are f-block elements with atomic numbers from 89 (actinium) to 103 (lawrencium), whereas ytterbium is a lanthanide with atomic number 70.
100. Which of the following is used in the preparation of photographic film?
A) Silver bromide
B) Copper sulfate
C) Zinc oxide
D) Chromium oxide
Answer: A
Explanation:
Silver bromide (AgBr) is used in the preparation of photographic film. It is light-sensitive and reacts when exposed to light, forming the basis for traditional black-and-white photography.
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