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41. Which of the following transition metals has the highest number of unpaired electrons in its +2 oxidation state?
A) Mn2+
B) Fe2+
C) Co2+
D) Ni2+
Answer: A
Explanation:
In the +2 oxidation state, manganese (Mn2+) has the highest number of unpaired electrons. Its electronic configuration is [Ar]3d5, with five unpaired electrons in the 3d subshell. More unpaired electrons lead to stronger paramagnetic properties.
42. Which of the following compounds contains an actinide element?
A) K2Cr2O7
B) UO2(NO3)2
C) FeSO4
D) CuSO4
Answer: B
Explanation:
UO2(NO3)2 (uranyl nitrate) contains uranium, which is an actinide element. Actinides are f-block elements that include elements like uranium, thorium, and plutonium.
43. Which of the following statements is correct about lanthanides?
A) Lanthanides are highly reactive metals
B) Lanthanides form complexes more readily than transition metals
C) Lanthanides are good conductors of electricity
D) Lanthanides exhibit a wide range of oxidation states
Answer: A
Explanation:
Lanthanides are highly reactive metals, especially when finely divided. They react readily with water, acids, and even oxygen. Despite this reactivity, lanthanides do not exhibit as wide a range of oxidation states as actinides, typically displaying the +3 oxidation state.
44. Which of the following is the correct statement about the electronic configuration of f-block elements?
A) Electrons are added to the d-orbitals
B) Electrons are added to the s-orbitals
C) Electrons are added to the f-orbitals
D) Electrons are added to the p-orbitals
Answer: C
Explanation:
In f-block elements, electrons are added to the f-orbitals. Specifically, in the lanthanide series, the 4f orbitals are being filled, while in the actinide series, the 5f orbitals are filled.
45. Which one of the following is not an alloy?
A) Brass
B) Bronze
C) Steel
D) Gallium
Answer: D
Explanation:
Gallium is a pure element, not an alloy. Brass (an alloy of copper and zinc), bronze (an alloy of copper and tin), and steel (an alloy of iron and carbon) are all alloys.
46. Which of the following ions shows maximum paramagnetism?
A) Cu+
B) Fe3+
C) Sc3+
D) Ti4+
Answer: B
Explanation:
Fe3+ shows the maximum paramagnetism because it has five unpaired electrons in its 3d subshell (3d53d5). Paramagnetism arises due to the presence of unpaired electrons, and the more unpaired electrons an ion has, the stronger the paramagnetic behavior.
47. Which of the following compounds is used as a catalyst in the contact process for the manufacture of sulfuric acid?
A) Platinum
B) Vanadium pentoxide
C) Nickel
D) Iron
Answer: B
Explanation:
Vanadium pentoxide (V2O5) is used as a catalyst in the contact process for the manufacture of sulfuric acid. It catalyzes the oxidation of sulfur dioxide (SO2) to sulfur trioxide (SO3), which is a key step in the production of sulfuric acid.
48. The most common oxidation state of uranium is:
A) +3
B) +4
C) +5
D) +6
Answer: D
49. The electronic configuration of Ce3+ is:
A) [Xe]4f2
B) [Xe]4f1
C) [Xe]4f0
D) [Xe]5d1
Answer: B
Explanation:
The electronic configuration of Ce3+ (cerium in the +3 oxidation state) is [Xe]4f1. Cerium has an atomic number of 58, and in the +3 oxidation state, it loses three electrons, leaving one electron in the 4f subshell.
50. The actinide series includes elements with atomic numbers from:
A) 57 to 70
B) 71 to 80
C) 89 to 103
D) 104 to 118
Answer: C
Explanation:
The actinide series includes elements with atomic numbers from 89 (actinium) to 103 (lawrencium). These elements are part of the f-block and are characterized by the filling of the 5f orbitals.
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