51. Which of the following is a property common to both lanthanides and actinides?
A) All are radioactive
B) They exhibit variable oxidation states
C) They are all non-metals
D) They do not form colored ions
Answer: B
Explanation:
Both lanthanides and actinides exhibit variable oxidation states. While lanthanides primarily show the +3 oxidation state, some also display +2 and +4 states. Actinides, on the other hand, exhibit a wider range of oxidation states, from +3 to +6 and beyond.
52. The compound [Fe(CN)6]4− is called:
A) Ferricyanide
B) Ferrocyanide
C) Ferrate
D) Ferricynate
Answer: B
Explanation:
The compound [Fe(CN)6]4− is called ferrocyanide. It consists of iron in the +2 oxidation state coordinated to six cyanide ions.
53. Which of the following statements is incorrect for lanthanides?
A) They are known for their high reactivity
B) They exhibit variable oxidation states
C) They show a decrease in atomic and ionic size with increasing atomic number
D) They are typically found in ores like monazite and bastnaesite
Answer: B
Explanation:
The statement that lanthanides exhibit variable oxidation states is incorrect. While they occasionally show +2 and +4 oxidation states, lanthanides predominantly exist in the +3 oxidation state.
54. Which of the following has the smallest atomic radius?
A) Lanthanum
B) Lutetium
C) Neodymium
D) Cerium
Answer: B
Explanation:
Lutetium (Lu) has the smallest atomic radius among the options because it is the last element in the lanthanide series. The lanthanide contraction causes the atomic and ionic radii to decrease progressively across the series.
55. Which element is the first in the 4d transition series?
A) Yttrium
B) Zirconium
C) Niobium
D) Technetium
Answer: A
Explanation:
Yttrium (Y) is the first element in the 4d transition series, with an atomic number of 39. The 4d transition series elements have electrons progressively filling the 4d subshell.
57. Which of the following transition metal oxides is used as a pigment in paints?
A) CuO
B) ZnO
C) Fe2O3
D) NiO
Answer: C
Explanation:
Fe2O3 (iron(III) oxide) is used as a pigment in paints. It gives a reddish-brown color and is commonly known as “red ochre.” It is one of the oldest pigments used by humans.
58. Which one of the following has the highest ionization energy?
A) Cr
B) Fe
C) Cu
D) Zn
Answer: D
Explanation:
ZnZn (zinc) has the highest ionization energy among the options because it has a completely filled d-subshell (3d103d10) and s-orbital (4s24s2), making it more stable and harder to remove an electron compared to the other elements.
59. Which of the following is true about the magnetic properties of lanthanides?
A) They are all diamagnetic
B) Most lanthanides are paramagnetic
C) Lanthanides do not show magnetic properties
D) Lanthanides are only magnetic in their solid form
Answer: B
Explanation:
Most lanthanides are paramagnetic because they have unpaired electrons in their 4f orbitals. The presence of these unpaired electrons leads to paramagnetism. The magnetic behavior varies depending on the number of unpaired electrons in the f-orbitals.
60. The stability of the Cu2+ ion in aqueous solution is due to:
A) Low ionization energy
B) High hydration energy
C) Low electron affinity
D) High lattice energy
Answer: B
Explanation:
The stability of the Cu2+ ion in aqueous solution is due to its high hydration energy. When Cu2+ dissolves in water, it becomes surrounded by water molecules, releasing significant hydration energy that stabilizes the ion.
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