Here below some basic MCQ’s about “d and f block elements” with answer which is explained in details. Let’s check one by one.
1. The general electronic configuration of d-block elements is:
A) (n−1)d1−10ns1−2
B) (n−1)d0−1ns2
C) (n−1)d1−5ns2
D) (n−1)d5−10ns1
Answer: A
Explanation:
The general electronic configuration of the d-block elements is (n−1)d1−10ns1−2. These elements have their last electron entering the (n-1)d orbital, while the ns orbital is also occupied. The specific distribution of electrons in d and s orbitals can vary among different elements within the d-block.
2. The color of transition metal complexes is due to:
A) Absorption of light in the infrared region
B) Unpaired electron transitions within the d-orbital
C) Paired electron transitions
D) Crystal field splitting of f-orbitals
Answer: B
Explanation:
The color of transition metal complexes arises due to the absorption of visible light that promotes an electron from one d-orbital to another (d-d transition). This happens because the energy difference between split d-orbitals corresponds to the energy of visible light. The absorbed wavelength corresponds to a particular color, and the complementary color is observed.
3. Which of the following d-block elements is not typically considered a transition metal?
A) Zinc
B) Iron
C) Copper
D) Chromium
Answer: A
Explanation:
Zinc is not considered a transition metal because its dd-orbital is completely filled in both its elemental state and its common oxidation state (+2). Transition metals, by definition, have an incomplete dd-subshell either in their elemental form or in one or more of their oxidation states.
4. Lanthanides and actinides are placed separately in the periodic table because:
A) They are non-metals
B) They belong to f-block elements
C) They have the same properties as transition elements
D) They do not fit into the periodic table
Answer: B
Explanation:
Lanthanides and actinides are placed separately at the bottom of the periodic table because they belong to the f-block elements. Their electrons are progressively filling the (n−2)f(n−2)f-orbitals, which is distinct from the d-block elements where the d-orbitals are filled.
5. Among the following, the compound that shows the highest paramagnetism is:
A) [Co(NH3)6]3+
B) [Fe(CN)6]3−
C) [Cu(NH3)4]2+
D) [Mn(CN)6]3−
Answer: D
Explanation:
Paramagnetism arises due to the presence of unpaired electrons. Manganese in [Mn(CN)6]3− is in the +3 oxidation state with an electronic configuration of 3d4. Since it has four unpaired electrons, it shows the highest paramagnetism among the given compounds.
6. The actinide contraction is greater than lanthanide contraction due to:
A) Greater shielding of 5f orbitals
B) Poorer shielding of 5f orbitals
C) Smaller nuclear charge
D) Smaller size of 5d orbitals
Answer: B
Explanation:
The actinide contraction is greater than the lanthanide contraction because the 5f orbitals in actinides shield the nuclear charge less effectively than the 4f orbitals in lanthanides. As a result, the electrons are more strongly attracted to the nucleus, leading to a greater contraction in atomic and ionic sizes across the actinide series.
7. The oxidation state of chromium in potassium dichromate K2Cr2O7 is:
A) +3
B) +4
C) +6
D) +2
Answer: C
Explanation:
In potassium dichromate, K2Cr2O7, the oxidation state of potassium (K) is +1, and oxygen (O) is -2. The sum of oxidation states in the compound must equal 0. Let the oxidation state of chromium (Cr) be x. We set up the equation: 2(+1)+2x+7(−2)=0 Solving gives x=+6x=+6, so the oxidation state of chromium is +6.
8. The most common oxidation state of lanthanides is:
A) +2
B) +3
C) +4
D) 0
Answer: B
Explanation:
Lanthanides most commonly exhibit an oxidation state of +3. This is because after losing three electrons (two from the 6s orbital and one from the 4f orbital), they attain a stable configuration with a half-filled or empty 4f subshell.
9. Which of the following metals can show a maximum oxidation state of +7?
A) Copper
B) Manganese
C) Iron
D) Cobalt
Answer: B
Explanation:
Manganese can exhibit a maximum oxidation state of +7, as seen in compounds like potassium permanganate (KMnO4). This is because manganese has a total of seven valence electrons that can be lost during oxidation.
10. The magnetic moment of a transition metal ion depends on:
A) The number of paired electrons
B) The number of unpaired electrons
C) Its atomic size
D) Its electron configuration in the outermost shell
Answer: B
Explanation:
The magnetic moment of a transition metal ion is directly related to the number of unpaired electrons. The more unpaired electrons, the greater the magnetic moment. This is typically calculated using the formula: μ=n(n+2)where n is the number of unpaired electrons.
11. Transition metals form colored compounds because:
A) They absorb light and re-emit it
B) d-d transitions of electrons
C) f-f transitions of electrons
D) They have paired electrons
Answer: B
Explanation:
Transition metals form colored compounds due to d-d transitions. When light is absorbed, electrons jump from a lower energy d-orbital to a higher energy one (d-d transition). The color observed is due to the wavelength of light that is not absorbed, which is the complementary color of the absorbed light.
12. Which of the following is not an f-block element?
A) Cerium
B) Thorium
C) Neodymium
D) Zinc
Answer: D
Explanation:
Zinc is not an f-block element; it belongs to the d-block. The f-block elements are lanthanides and actinides, where electrons are filling the 4f or 5f orbitals.
13. The element with atomic number 57 belongs to which block of the periodic table?
A) s-block
B) p-block
C) d-block
D) f-block
Answer: D
Explanation:
The element with atomic number 57 is lanthanum (La), and it is the first element of the f-block, specifically starting the lanthanide series. Lanthanum itself, however, is often placed in the d-block but marks the beginning of the f-block.
14. Which of the following ions is colorless in aqueous solution?
A) Cu2+
B) Fe3+
C) Zn2+
D) Co2+
Answer: C
Explanation:
Zn2+ is colorless in aqueous solution because it has a completely filled d-subshell (3d¹⁰). Since there are no unpaired d-electrons, it cannot undergo d-d transitions, which are responsible for color in transition metal ions.
15. Which of the following compounds will exhibit the strongest magnetic properties?
A) [Ti(H2O)6]3+
B) [Cu(NH3)4]2+
C) [Fe(CN)6]4−
D) [MnO4]−
Answer: D
Explanation:
[MnO4]− (permanganate ion) contains manganese in the +7 oxidation state. Although this particular ion does not exhibit strong magnetic properties because there are no unpaired electrons in Mn⁷⁺, the magnetic properties depend on the specific electronic configuration. Among the options, [Ti(H2O)6]3+ has the most unpaired electrons, thus exhibiting stronger paramagnetism.
16. The f-block elements are also known as:
A) Transition metals
B) Inner transition metals
C) Heavy metals
D) Alkali metals
Answer: B
Explanation:
The f-block elements are referred to as “inner transition metals” because their f-orbitals are progressively filled as you move across the period, and they are located separately from the main body of the periodic table.
17. The first transition series includes elements from:
A) Scandium to Copper
B) Titanium to Zinc
C) Vanadium to Manganese
D) Chromium to Nickel
Answer: A
Explanation:
The first transition series includes the elements from scandium (Z = 21) to copper (Z = 29). These elements have partially filled 3d orbitals and exhibit typical properties of transition metals such as variable oxidation states and the formation of colored compounds.
18. Which of the following lanthanide ions is colorless?
A) Ce4+
B) Eu3+
C) Tb3+
D) Pr3+
Answer: A
Explanation:
Ce4+Ce4+ is colorless because it has no f-electrons. In its +4 oxidation state, cerium has an empty 4f subshell, and therefore, it cannot undergo f-f transitions, which are responsible for the color of lanthanide ions.
19. Which of the following is an alloy of copper and zinc?
A) Brass
B) Bronze
C) Steel
D) Nichrome
Answer: A
Explanation:
Brass is an alloy of copper and zinc. It is commonly used in applications requiring corrosion resistance and malleability.
20. The stability of the +3 oxidation state decreases in the sequence:
A) Sc>Ti>V>Cr>Mn
B) Mn>Cr>V>Ti>Sc
C) V>Cr>Mn>Ti>Sc
D) Sc>V>Mn>Cr>Ti
Answer: A
Explanation:
The stability of the +3 oxidation state decreases in the sequence Sc>Ti>V>Cr>. As we move across the 3d series, the energy required to remove electrons from the d-orbitals increases, and higher oxidation states become less stable compared to lower ones.
21. Which of the following d-block elements does not show variable oxidation states?
A) Zn
B) Fe
C) Ni
D) Co
Answer: A
Explanation:
Zinc (Zn) does not show variable oxidation states; it exhibits only a +2 oxidation state in its compounds because its dd-subshell is completely filled (3d¹⁰), and it cannot lose or gain more electrons to exhibit other oxidation states.
22. The shielding effect of 4f electrons in lanthanides is:
A) Very effective
B) Less effective than 5d electrons
C) More effective than 3d electrons
D) Poorly effective
Answer: D
Explanation:
The 4f electrons in lanthanides have a very poor shielding effect because they are more deeply buried within the atom, and the penetration of their electron cloud is less significant. This leads to an increase in the effective nuclear charge experienced by the outer electrons.
23. The most common oxidation state for actinides is:
A) +2
B) +3
C) +4
D) +5
Answer: B
Explanation:
The most common oxidation state for actinides is +3, similar to lanthanides. However, actinides also show a wide variety of oxidation states due to their ability to lose electrons from both 5f and 6d orbitals.
24. Transition metals form complexes due to:
A) Small size and high charge
B) Ability to donate electrons
C) Large atomic size
D) Inability to form bonds with ligands
Answer: A
Explanation:
Transition metals form complexes because they have a small size and high charge, which allows them to attract ligands (species that donate electron pairs) and form stable complexes. Their partially filled d-orbitals also play a crucial role in complex formation.
25. Which of the following statements is correct about the magnetic properties of transition metals?
A) All transition metals are diamagnetic
B) Transition metals have magnetic moments due to unpaired electrons
C) Transition metals do not have magnetic properties
D) Magnetic properties of transition metals are due to paired electrons
Answer: B
Explanation:
Transition metals exhibit magnetic properties due to the presence of unpaired electrons in their d-orbitals. These unpaired electrons generate a magnetic moment, leading to paramagnetism. The more unpaired electrons, the stronger the magnetic properties.
26. Which of the following ions is likely to be colorless in solution?
A) Fe2+
B) Cu2+
C) Zn2+
D) Ni2+
Answer: C
Explanation:
The Zn2+ ion is colorless in solution because it has a completely filled d-subshell (3d¹⁰). Since there are no unpaired electrons, d-d transitions that would result in color cannot occur, making it colorless.
27. The ability of transition metals to form complexes is due to:
A) Their large atomic size
B) Their tendency to lose electrons easily
C) The presence of vacant d-orbitals
D) Their high electropositivity
Answer: C
Explanation:
Transition metals have vacant d-orbitals that can accept electron pairs from ligands to form coordination complexes. This ability to form complexes is one of the characteristic properties of transition metals.
28. The actinides show a greater range of oxidation states compared to lanthanides because:
A) Their 5f orbitals are more diffused
B) They have more valence electrons
C) They form stronger bonds with ligands
D) Their atomic radii are smaller
Answer: A
Explanation:
The 5f orbitals in actinides are more diffused compared to the 4f orbitals in lanthanides. This allows actinides to have a greater range of oxidation states, as electrons from both the 5f and 6d orbitals can participate in bonding.
29. Which of the following elements is not part of the first transition series?
A) Scandium
B) Chromium
C) Copper
D) Palladium
Answer: D
Explanation:
Palladium (Pd) is part of the second transition series, not the first. The first transition series includes elements from Scandium (Z = 21) to Copper (Z = 29), while Palladium belongs to the series starting from Yttrium (Z = 39).
30. Which of the following oxides is amphoteric?
A) Cr2O3
B) Mn2O7
C) ZnO
D) Fe2O3
Answer: A
Explanation:
Cr2O3Cr2O3 (chromium(III) oxide) is an amphoteric oxide, meaning it can react with both acids and bases. Amphoteric oxides can behave as both acidic and basic oxides depending on the reaction environment.
31. In the preparation of potassium dichromate from chromite ore, the oxidation state of chromium changes from:
A) +2 to +6
B) +3 to +6
C) +6 to +3
D) +2 to +3
Answer: B
Explanation:
In the preparation of potassium dichromate (K2Cr2O7) from chromite ore (FeCr2O4), chromium changes its oxidation state from +3 in chromite to +6 in dichromate. This involves an oxidation process in which chromium is converted from its +3 oxidation state to the +6 state.
32. Lanthanide contraction is responsible for:
A) The similarity in the atomic radii of the second and third transition series
B) The higher melting point of lanthanides
C) The color of lanthanide ions
D) The paramagnetic behavior of lanthanides
Answer: A
Explanation:
Lanthanide contraction refers to the steady decrease in the ionic radii of the lanthanides as you move across the series. This is due to the poor shielding effect of the 4f electrons. As a result, the atomic and ionic sizes of the second and third transition series become very similar, which influences their chemical properties.
33. Which of the following is true about actinides compared to lanthanides?
A) Actinides have lower atomic numbers
B) Actinides have more variable oxidation states
C) Actinides are more stable than lanthanides
D) Actinides do not form complexes
Answer: B
Explanation:
Actinides have more variable oxidation states compared to lanthanides. While lanthanides predominantly exhibit a +3 oxidation state, actinides can show a wide range of oxidation states (+3, +4, +5, +6, and even +7), due to the involvement of 5f, 6d, and 7s orbitals.
34. The catalytic properties of transition metals are due to:
A) Their high melting points
B) Their ability to adopt multiple oxidation states
C) Their large atomic radii
D) Their poor conductivity
Answer: B
Explanation:
Transition metals are excellent catalysts because they can adopt multiple oxidation states, which allows them to facilitate oxidation-reduction reactions. Their partially filled d-orbitals can also form temporary bonds with reactants, providing a surface for the reaction to occur more efficiently.
35. Which of the following elements is used as a catalyst in the Haber process for ammonia synthesis?
A) Iron
B) Nickel
C) Zinc
D) Copper
Answer: A
Explanation:
Iron is used as a catalyst in the Haber process for the synthesis of ammonia. The iron catalyst helps to speed up the reaction between nitrogen and hydrogen to form ammonia (NH3NH3) by providing a surface for the reaction and lowering the activation energy.
36. The ionic radii of lanthanides:
A) Increase across the period
B) Decrease across the period
C) Remain constant
D) First increase and then decrease
Answer: B
Explanation:
The ionic radii of lanthanides decrease steadily across the period from lanthanum to lutetium. This decrease is known as the lanthanide contraction and is due to the poor shielding effect of the 4f electrons, which causes the outer electrons to be more strongly attracted to the nucleus.
37. The element with the atomic number 92 belongs to which group of the periodic table?
A) d-block
B) p-block
C) s-block
D) f-block
Answer: D
Explanation:
The element with atomic number 92 is uranium, which belongs to the f-block of the periodic table. Uranium is an actinide and its electrons are filling the 5f orbital.
38. Which of the following shows the least tendency to form complexes?
A) Cu2+
B) Fe3+
C) Zn2+
D) Co3+
Answer: C
Explanation:
Zn2+ shows the least tendency to form complexes because its 3d orbital is completely filled (3d¹⁰). It does not have available d-orbitals to accept electron pairs from ligands, making it less likely to form coordination compounds compared to other transition metals.
39. The metal in [Ni(CN)4]2− has the following hybridization:
A) sp2
B) sp3
C) dsp2
D) d2sp3
Answer: C
Explanation:
In [Ni(CN)4]2−, the nickel ion is in a square planar geometry, which corresponds to dsp2dsp2 hybridization. This hybridization occurs when one d-orbital, one s-orbital, and two p-orbitals are mixed to form four hybrid orbitals for bonding.
40. The most common oxidation state of the first series of transition elements is:
A) +1
B) +2
C) +3
D) +4
Answer: B
Explanation:
The most common oxidation state of the first series of transition elements is +2. This occurs because they tend to lose the two electrons from their outermost s-orbital, leading to a +2 oxidation state in many of their compounds.
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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.
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.
61. Which of the following is the main reason for the complex formation tendency of d-block elements?
A) High electronegativity
B) Low atomic radii
C) Availability of vacant d-orbitals
D) Large ionic radii
Answer: C
Explanation:
The main reason for the complex formation tendency of d-block elements is the availability of vacant d-orbitals. These orbitals can accept electron pairs from ligands, allowing d-block elements to form a variety of coordination complexes.
62. Which of the following pairs of elements shows similar chemical properties due to lanthanide contraction?
A) Zr and Hf
B) Nb and Ta
C) Mo and W
D) Ti and Zr
Answer: A
Explanation:
Zirconium (Zr) and hafnium (Hf) show similar chemical properties due to lanthanide contraction. The lanthanide contraction causes the atomic and ionic radii of Hf to be nearly the same as Zr, leading to similar chemical behavior.
63. Which of the following is true about KMnO4 in acidic medium?
A) It acts as a reducing agent
B) Manganese is reduced to Mn2+
C) Manganese remains in the +7 oxidation state
D) It is colorless in solution
Answer: B
Explanation:
In acidic medium, KMnO4 (potassium permanganate) acts as an oxidizing agent, and manganese is reduced from its +7 oxidation state to Mn2+. This reduction is responsible for the disappearance of the purple color of KMnO4 in solution.
64. Which of the following is a correct statement about the coordination number of a metal in a complex?
A) It is always 4
B) It is the number of ligands attached to the metal
C) It is the charge of the metal ion
D) It is the number of valence electrons in the metal
Answer: B
Explanation:
The coordination number of a metal in a complex refers to the number of ligands attached to the central metal ion. For example, in the complex [Cu(NH3)4]2+, the coordination number of copper is 4.
65. Which one of the following is the most stable oxidation state of cerium?
A) +2
B) +3
C) +4
D) +6
Answer: B
Explanation:
The most stable oxidation state of cerium is +3. Cerium can also exist in the +4 oxidation state, but the +3 state is more stable due to the configuration of its f-electrons.
66. Which one of the following is a property of actinides but not of lanthanides?
A) They form colored compounds
B) They show variable oxidation states
C) They exhibit paramagnetism
D) They are all radioactive
Answer: D
Explanation:
All actinides are radioactive, while only some lanthanides exhibit radioactivity. This property distinguishes the actinides from the lanthanides. Actinides, especially the heavier ones, undergo radioactive decay.
67. In the extraction of copper from copper pyrites, the role of silica is to:
A) Reduce the copper oxide
B) Oxidize the copper sulfide
C) Remove impurities of iron
D) Act as a catalyst
Answer: C
Explanation:
In the extraction of copper from copper pyrites (CuFeS2), silica acts as a flux to remove impurities of iron. Silica reacts with iron oxides to form iron silicate (FeSiO3), which is removed as slag.
68. The main ore of thorium is:
A) Monazite
B) Cassiterite
C) Bauxite
D) Galena
Answer: A
Explanation:
The main ore of thorium is monazite. Monazite is a phosphate mineral that contains rare earth elements and thorium, which is extracted for use in nuclear reactors and other applications.
69. Which of the following is a characteristic of f-block elements?
A) They have high electronegativity
B) They show multiple oxidation states
C) They do not form compounds with non-metals
D) They have no magnetic properties
Answer: B
Explanation:
A characteristic of f-block elements is that they show multiple oxidation states. This is due to the availability of 4f or 5f orbitals, which participate in bonding and allow these elements to exhibit variable oxidation states.
70. Which of the following ions is expected to have the smallest size?
A) Sc3+
B) Fe3+
C) Zn2+
D) Mn2+
Answer: A
Explanation:
Sc3+ (scandium in the +3 oxidation state) is expected to have the smallest size because it has the highest effective nuclear charge for a given number of electrons. This results in a stronger attraction of electrons towards the nucleus, leading to a smaller ionic radius.
72. Which one of the following ions has the largest number of unpaired electrons?
A) Fe2+
B) Mn2+
C) Cr3+
D) Co2+
Answer: B
Explanation:
Mn2+ (manganese in the +2 oxidation state) has five unpaired electrons in the 3d5 configuration, which is the maximum number of unpaired electrons possible in a d-block element in the +2 oxidation state.
73. Which of the following lanthanides is known for its ability to absorb neutrons and is used in nuclear reactors?
A) Samarium
B) Dysprosium
C) Neodymium
D) Gadolinium
Answer: D
Explanation:
Gadolinium (Gd) is known for its ability to absorb neutrons and is used in nuclear reactors as a control material. It has a high neutron absorption cross-section, making it effective in controlling nuclear reactions.
74. Which of the following is the strongest oxidizing agent?
A) MnO4−
B) Cr2O72−
C) ClO4−
D) NO3−
Answer: A
Explanation:
MnO4− (permanganate ion) is the strongest oxidizing agent among the options. In acidic conditions, MnO4− is reduced to Mn2+, and this reduction releases a large amount of energy, making it a powerful oxidizer.
75. Which of the following transition elements shows the highest melting point?
A) Titanium
B) Chromium
C) Iron
D) Tungsten
Answer: D
Explanation:
Tungsten (W) has the highest melting point of all transition metals, around 3422°C. This property makes it useful in applications where high-temperature resistance is required, such as in filaments for light bulbs and heating elements.
76. In which of the following processes is vanadium pentoxide (V2O5) used as a catalyst?
A) Contact process
B) Haber process
C) Solvay process
D) Ostwald process
Answer: A
Explanation:
Vanadium pentoxide (V2O5 is used as a catalyst in the contact process for the production of sulfuric acid. It catalyzes the oxidation of sulfur dioxide (SO2) to sulfur trioxide (SO3).
77. Which of the following statements is correct for the d-block elements?
A) They are all non-metals
B) They show a wide range of oxidation states
C) They do not form colored compounds
D) They are poor conductors of electricity
Answer: B
Explanation:
D-block elements show a wide range of oxidation states due to the involvement of their d-electrons in bonding. This is one of the key characteristics of transition metals, leading to diverse chemical properties and the formation of coordination complexes.
78. Which of the following is used as a moderator in nuclear reactors?
A) Lead
B) Graphite
C) Thorium
D) Beryllium
Answer: B
Explanation:
Graphite is used as a moderator in nuclear reactors. Moderators slow down fast neutrons, making them more effective in sustaining a controlled nuclear chain reaction.
79. The color of Cr3+ ions in aqueous solution is:
A) Yellow
B) Green
C) Red
D) Blue
Answer: B
Explanation:
Cr3+ ions in aqueous solution are typically green in color. The color arises due to d-d transitions, where electrons move between energy levels within the d-orbitals in the presence of ligands such as water molecules.
80. Which of the following is an actinide element?
A) Lutetium
B) Thorium
C) Gadolinium
D) Ytterbium
Answer: B
Explanation:
Thorium (Th) is an actinide element. Actinides are f-block elements that include elements with atomic numbers from 89 to 103, and thorium is one of the lighter actinides, used in nuclear reactors.
81. Which of the following is not a characteristic property of d-block elements?
A) High melting and boiling points
B) Formation of colored compounds
C) Low density
D) Formation of complex compounds
Answer: C
Explanation:
Low density is not a characteristic property of d-block elements. In fact, many d-block elements are known for their high density, in addition to high melting and boiling points, the formation of colored compounds, and complex compound formation.
82. The lanthanide contraction is responsible for which of the following?
A) Decrease in atomic radii across the lanthanide series
B) Increase in ionic radii across the lanthanide series
C) Decrease in melting points of lanthanides
D) Increase in atomic radii across the lanthanide series
Answer: A
Explanation:
The lanthanide contraction refers to the gradual decrease in atomic and ionic radii across the lanthanide series. This is caused by poor shielding of the 4f electrons, resulting in a stronger attraction of electrons to the nucleus as the atomic number increases.
83. Which of the following is a use of zirconium in industry?
A) As a pigment in white paints
B) As a moderator in nuclear reactors
C) In the production of stainless steel
D) As a catalyst in the Haber process
Answer: B
Explanation:
Zirconium is used as a moderator in nuclear reactors. It is preferred due to its low absorption of neutrons, which helps maintain the controlled chain reactions necessary for the production of nuclear energy.
84. Which of the following ions is expected to have the smallest radius?
A) Zr4+
B) Ti4+
C) Hf4+
D) Ce4+
Answer: C
Explanation:
Hf4+ (hafnium in the +4 oxidation state) is expected to have the smallest radius due to the lanthanide contraction, which causes elements like hafnium to have significantly smaller radii than expected for their position in the periodic table.
85. Which of the following elements is used in the manufacture of permanent magnets?
A) Cerium
B) Neodymium
C) Europium
D) Samarium
Answer: B
Explanation:
Neodymium (Nd) is used in the manufacture of powerful permanent magnets. These neodymium magnets are widely used in electronics, motors, and other applications requiring strong magnetic fields.
86. Which of the following compounds is a common ore of chromium?
A) Hematite
B) Bauxite
C) Chromite
D) Galena
Answer: C
Explanation:
Chromite (FeCr2O4FeCr2O4) is a common ore of chromium. It is the primary source of chromium for the production of stainless steel, alloys, and chrome plating.
87. The oxidation state of iron in Fe(CO)5Fe(CO)5 is:
A) +1
B) +2
C) 0
D) -1
Answer: C
Explanation:
The oxidation state of iron in Fe(CO)5Fe(CO)5 (iron pentacarbonyl) is 0. Carbon monoxide is a neutral ligand, so the oxidation state of iron remains unchanged in this complex.
88. Which of the following oxides of iron is commonly known as rust?
A) Fe2O3
B) FeO
C) Fe3O4
D) FeS2
Answer: A
Explanation:
Fe2O3 (iron(III) oxide) is commonly known as rust when it is hydrated. Rust is a reddish-brown substance formed when iron reacts with oxygen and moisture in the air.
89. Which of the following statements is true for the f-block elements?
A) They are all diamagnetic
B) They exhibit similar chemical properties due to similar ionic radii
C) They show a large variation in their atomic and ionic sizes
D) They have high ionization energies
Answer: B
Explanation:
F-block elements exhibit similar chemical properties because they have similar ionic radii, especially within the lanthanide series, where the ionic radii decrease gradually due to lanthanide contraction. This leads to similar reactivity and chemical behavior.
90. In which of the following oxidation states does uranium exhibit the highest stability in aqueous solution?
A) +3
B) +4
C) +5
D) +6
Answer: D
Explanation:
Uranium in the +6 oxidation state is the most stable in aqueous solutions. In this state, it typically exists as the UO22+ ion (uranyl ion), which is very stable and forms the basis for most uranium chemistry in solution.
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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