CBSE Class 12 Chemistry D And F Block Elements Question Bank Set B

Question. K₂Cr₂O₇ on heating with aqueous NaOH gives
(a) Cr₂O₇^2–
(b) Cr(OH)₂
(c) CrO₄^2–
(d) Cr(OH)₃ 
Answer. C

Question. KMnO₄ reacts with oxalic acid according to the equation
2MnO₄^– + 5C₂O₄^2– + 16H⁺→ 2Mn²⁺ + 10CO₂ + 8H₂O
Here 20 mL of 0.1 M KMnO₄ is equivalent to
(a) 50 mL of 0.5 M C₂H₂O₄
(b) 20 mL of 0.1 M C₂H₂O₄
(c) 20 mL of 0.5 M C₂H₂O₄
(d) 50 mL of 0.1 M C₂H₂O₄
Answer. D

Question. The oxidation state of Cr in K₂Cr₂O₇ is
(a) +5
(b) +3
(c) +6
(d) +7 
Answer. C

Question. Which one of the following statements related to lanthanons is incorrect?
(a) Europium shows +2 oxidation state.
(b) The basicity decreases as the ionic radius decreases from Pr to Lu.
(c) All the lanthanons are much more reactive than aluminium.
(d) Ce(+4) solutions are widely used as oxidizing agent in volumetric analysis. 
Answer. C

Question. The electronic configurations of Eu (Atomic No. 63), Gd (Atomic No. 64) and Tb (Atomic No. 65) are
(a) [Xe]4f ⁶5d¹6s², [Xe]4f ⁷5d¹6s² and [Xe]4f ⁸5d¹6s²
(b) [Xe]4f ⁷ 6s², [Xe]4f ⁷ 5d¹ 6s² and [Xe]4f ⁹ 6s²
(c) [Xe]4f ⁷ 6s², [Xe]4f ⁸ 6s² and [Xe]4f ⁸ 5d¹ 6s²
(d) [Xe]4f ⁶ 5d¹ 6s², [Xe]4f ⁷ 5d¹ 6s² and [Xe]4f ⁹ 6s²
Answer. B

Question. Gadolinium belongs to 4f series. Its atomic number is 64. Which of the following is the correct electronic configuration of gadolinium?
(a) [Xe] 4f ⁹ 5s¹
(b) [Xe] 4f ⁷5d¹6s²
(c) [Xe] 4f ⁶5d²6s²
(d) [Xe] 4f ⁸6d²
Answer. B

Question. Because of lanthanoid contraction, which of the following pairs of elements have nearly same atomic radii? (Numbers in the parenthesis are atomic numbers)
(a) Zr(40) and Hf(72)
(b) Zr(40) and Ta(73)
(c) Ti(22) and Zr(40)
(d) Zr(40) and Nb(41)
Answer. A

Question. Reason of lanthanoid contraction is
(a) negligible screening effect of ‘f ’-orbitals
(b) increasing nuclear charge
(c) decreasing nuclear charge
(d) decreasing screening effect.
Answer. A

Question. Which of the following lanthanoid ions is diamagnetic?
(At. nos. Ce = 58, Sm = 62, Eu = 63, Yb = 70)
(a) Eu²⁺
(b) Yb²⁺
(c) Ce²⁺
(d) Sm²⁺
Answer. B

Question. Which of the following oxidation states is the most common among the lanthanoids?
(a) 4
(b) 2
(c) 5
(d) 3
Answer. D

Question. Identify the incorrect statement among the following :
(a) Lanthanoid contraction is the accumulation of successive shrinkages.
(b) As a result of lanthanoid contraction, the properties of 4d series of the transition elements have no similarities with the 5d series of elements.
(c) Shielding power of 4f electrons is quite weak.
(d) There is a decrease in the radii of the atoms or ions as one proceeds from La to Lu. 
Answer. B

Question. Lanthanoids are
(a) 14 elements in the sixth period (atomic no. 90 to 103) that are filling 4f sublevel
(b) 14 elements in the seventh period (atomic number = 90 to 103) that are filling 5f sublevel
(c) 14 elements in the sixth period (atomic number = 58 to 71) that are filling the 4f sublevel
(d) 14 elements in the seventh period (atomic number = 58 to 71) that are filling 4f sublevel.
Answer. C

Question. The correct order of ionic radii of Y³⁺, La³⁺, Eu³⁺ and
Lu³⁺ is (At. nos. Y = 39, La = 57, Eu = 63, Lu = 71)
(a) Y³⁺ < La³⁺ < Eu³⁺ < Lu³⁺
(b) Y³⁺ < Lu³⁺ < Eu³⁺ < La³⁺
(c) Lu³⁺ < Eu³⁺ < La³⁺ < Y³⁺
(d) La³⁺ < Eu³⁺ < Lu³⁺ < Y³⁺
Answer. B

Question. General electronic configuration of lanthanides is
(a) (n – 2) f^{1 – 14} (n – 1) s²p6d^{0 – 1} ns²
(b) (n – 2) f^{10 – 14} (n – 1) d^{0 – 1} ns²
(c) (n – 2) f ^{0 – 14} (n – 1) d¹⁰ ns²
(d) (n – 2) d^{0 – 1} (n – 1) f^{1 – 14} ns² 
Answer. A

Question. Which of the following statement is not correct?
(a) La(OH)₃ is less basic than Lu(OH)₃.
(b) In lanthanide series ionic radius of Ln⁺³ ion decreases.
(c) La is actually an element of transition series rather lanthanides.
(d) Atomic radius of Zn and Hf are same because of lanthanide contraction.
Answer. A

Question. The lanthanide contraction is responsible for the fact that
(a) Zr and Hf have about the same radius
(b) Zr and Zn have the same oxidation state
(c) Zr and Y have about the same radius
(d) Zr and Nb have similar oxidation state. 
Answer. A

Question. Which of the following statements concerning lanthanide elements is false?
(a) All lanthanides are highly dense metals.
(b) More characteristic oxidation state of lanthanide elements is +3.
(c) Lanthanides are separated from one another by ion exchange method.
(d) Ionic radii of trivalent lanthanides steadily increases with increase in the atomic number.
Answer. D

Question. The reason for greater range of oxidation states in actinoids is attributed to
(a) actinoid contraction
(b) 5f, 6d and 7s levels having comparable energies
(c) 4f and 5d levels being close in energies
(d) the radioactive nature of actinoids.
Answer. B

Question. Which of the following exhibits only +3 oxidation state?
(a) U
(b) Th
(c) Ac
(d) Pa 
Answer. C

Question. More number of oxidation states are exhibited by the actinoids than by the lanthanoids. The main reason for this is
(a) more active nature of the actinoids
(b) more energy difference between 5f and 6d orbitals than that between 4f and 5d orbitals
(c) lesser energy difference between 5f and 6d orbitals than that between 4f and 5d orbitals
(d) greater metallic character of the lanthanoids than that of the corresponding actinoids.
Answer. C

Question. Which one of the following elements shows maximum number of different oxidation states in its compounds?
(a) Gd
(b) La
(c) Eu
(d) Am 
Answer. D

Question. Match the catalyst with the process : Catalyst Process
(i) V₂O₅                     (p) The oxidation of ethyne to ethanal
(ii) TiCl₄ +Al(CH₃)₃   (q) Polymerisation of alkynes
(iii) PdCl₂                  (r) Oxidation of SO₂ in the manufacture of H₂SO₄
(iv) Nickel                 (s) Polymerisation complexes of ethylene
Which of the following is the correct option?
(a) (i)-(r), (ii)-(s), (iii)-(p), (iv)-(q)
(b) (i)-(p), (ii)-(q), (iii)-(r), (iv)-(s)
(c) (i)-(p), (ii)-(r), (iii)-(q), (iv)-(s)
(d) (i)-(r), (ii)-(p), (iii)-(s), (iv)-(q)
Answer. A

Question. HgCl₂ and I₂ both when dissolved in water containing I^– ions, the pair of species formed is
(a) HgI₂, I^–
(b) HgI₄^2–, I₃^–
(c) Hg₂I₂, I^–
(d) HgI₂, I₃^–
Answer. B

Question. Which of the following elements is responsible for oxidation of water to O₂ in biological processes?
(a) Cu
(b) Mo
(c) Fe
(d) Mn 
Answer. C

Question. When calomel reacts with NH4OH, we get
(a) Hg₂O
(b) HgO
(c) HgNH₂Cl
(d) NH₂–Hg–Hg–Cl
Answer. C

Question. Photographic films and plates have an essential ingredient of
(a) silver nitrate
(b) silver bromide
(c) sodium chloride
(d) oleic acid.
Answer. B

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