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

Question. Sc (Z = 21) is a transition element but Zn (Z = 30) is not because
(a) both Sc³⁺ and Zn²⁺ ions are colourless and form white compounds
(b) in case of Sc, 3d orbitals are partially filled but in Zn these are filled
(c) last electron is assumed to be added to 4s level in case of Zn
(d) both Sc and Zn do not exhibit variable oxidation states 
Answer. B

Question. Which of the following ions has electronic configuration [Ar]3d⁶?
(a) Ni³⁺
(b) Mn³⁺
(c) Fe³⁺
(d) Co³⁺
(At. nos. Mn = 25, Fe = 26, Co = 27, Ni = 28) 
Answer. D

Question. Among the following series of transition metal ions, the one where all metal ions have 3d² electronic configuration is
[At. nos. Ti = 22, V = 23, Cr = 24, Mn = 25]
(a) Ti³⁺, V²⁺, Cr³⁺, Mn⁴⁺
(b) Ti⁺, V⁴⁺, Cr⁶⁺, Mn⁷⁺
(c) Ti⁴⁺, V³⁺, Cr²⁺, Mn³⁺
(d) Ti²⁺, V³⁺, Cr⁴⁺, Mn⁵⁺
Answer. D

Question. Which of the following configuration is correct for iron?
(a) 1s²2s²2p⁶3s²3p⁶4s²3d⁷
(b) 1s²2s²2p⁶3s²3p⁶4s²3d⁵
(c) 1s²2s²2p⁶3s²3p⁶3d⁵
(d) 1s²2s²2p⁶3s²3p⁶4s²3d⁶
Answer. D

Question. Which of the following has more unpaird d-electrons?
(a) N³⁺
(b) Fe²⁺
(c) Zn⁺
(d) Cu⁺
Answer. B

Question. The electronic configuration of transition elements is exhibited by
(a) ns¹
(b) ns²np⁵
(c) ns² (n – 1)d^1–10
(d) ns² (n – 1)d¹⁰
Answer. C

Question. The electronic configurations of four elements are given below. Which element does not belong to the same family as others?
(a) [Xe]4f¹⁴5d¹⁰6s²
(b) [Kr]4d¹⁰5s²
(c) [Ne]3s²3p⁵
(d) [Ar]3d¹⁰4s² 
Answer. C

Question. Identify the incorrect statement.
(a) Cr²⁺ (d⁴) is a stronger reducing agent than Fe²⁺ (d⁶) in water.
(b) The transition metals and their compounds are known for their catalytic activity due to their ability to adopt multiple oxidation states and to form complexes.
(c) Interstitial compounds are those that are formed when small atoms like H, C or N are trapped inside the crystal lattices of metals.
(d) The oxidation states of chromium in CrO₄ ^2– and Cr₂O₇ ^2– are not the same. 
Answer. D

Question. The calculated spin only magnetic moment of Cr²⁺ ion is
(a) 3.87 BM
(b) 4.90 BM
(c) 5.92 BM
(d) 2.84 BM
Answer. B

Question. Match the metal ions given in Column-I with the spin magnetic moments of the ions given in Column-II and assign the correct code :
Column-I       Column-II
A. Co³⁺         (i) √8 B.M.
B. Cr³⁺         (ii) √35 B.M.
C. Fe³⁺         (iii) √3 B.M.
D. Ni²⁺         (iv) √24 B.M.
                     (v) √15 B.M.
      A   B   C   D
(a) (iv) (v) (ii) (i)
(b) (i) (ii) (iii) (iv)
(c) (iv) (i) (ii) (iii)
(d) (iii) (v) (i) (ii) 
Answer. A

Question. Magnetic moment 2.84 B.M. is given by
(At. nos. Ni = 28, Ti = 22, Cr = 24, Co = 27)
(a) Cr²⁺
(b) Co²⁺
(c) Nⁱ²⁺
(d) Ti³⁺
Answer. C

Question. Which of the following processes does not involve oxidation of iron?
(a) Formation of Fe(CO)₅ from Fe.
(b) Liberation of H2 from steam by iron at high temperature.
(c) Rusting of iron sheets.
(d) Decolourisation of blue CuSO₄ solution by iron. 
Answer. A

Question. Which of the following statements about the interstitial compounds is incorrect?
(a) They are much harder than the pure metal.
(b) They have higher melting points than the pure metal.
(c) They retain metallic conductivity.
(d) They are chemically reactive. 
Answer. D

Question. Identify the alloy containing a non-metal as a constituent in it.
(a) Invar
(b) Steel
(c) Bell metal
(d) Bronze 
Answer. B

Question. The catalytic activity of transition metals and their compounds is ascribed mainly to
(a) their magnetic behaviour
(b) their unfilled d-orbitals
(c) their ability to adopt variable oxidation states
(d) their chemical reactivity. 
Answer. C

Question. Which one of the following does not correctly represent the correct order of the property indicated against it?
(a) Ti < V < Cr < Mn; increasing number of oxidation states
(b) Ti³⁺ < V³⁺ < Cr³⁺ < Mn³⁺ : increasing magnetic moment
(c) Ti < V < Cr < Mn : increasing melting points
(d) Ti < V < Mn < Cr : increasing 2nd ionization enthalpy 
Answer. C

Question. Four successive members of the first series of the transition metals are listed below. For which one of them the standard potential (E°_M²⁺/M) value has a positive sign?
(a) Co (Z = 27)
(b) Ni (Z = 28)
(c) Cu (Z = 29)
(d) Fe (Z = 26)
Answer. C

Question. For the four successive transition elements (Cr, Mn,Fe and Co), the stability of +2 oxidation state will be there in which of the following order?
(a) Mn > Fe > Cr > Co
(b) Fe > Mn > Co > Cr
(c) Co > Mn > Fe > Cr
(d) Cr > Mn > Co > Fe
(At. nos. Cr = 24, Mn = 25, Fe = 26, Co = 27) 
Answer. A

Question. Which of the following ions will exhibit colour in aqueous solutions?
(a) La³⁺ (Z = 57)
(b) Ti³⁺ (Z = 22)
(c) Lu³⁺ (Z = 71)
(d) Sc³⁺ (Z = 21)
Answer. B

Question. Which of the following pairs has the same size?
(a) Fe²⁺, Ni²⁺
(b) Zr⁴⁺, Ti⁴⁺
(c) Zr⁴⁺, Hf⁴⁺
(d) Zn²⁺, Hf⁴⁺ 
Answer. C

Question. Which one of the elements with the following outer orbital configurations may exhibit the largest number of oxidation states?
(a) 3d⁵4s¹
(b) 3d⁵4s²
(c) 3d²4s²
(d) 3d³4s² 
Answer. B

Question. The correct order of decreasing second ionisation enthalpy of Ti(22), V(23), Cr(24) and Mn(25) is
(a) Mn > Cr > Ti > V
(b) Ti > V > Cr > Mn
(c) Cr > Mn > V > Ti
(d) V > Mn > Cr > Ti
Answer. C

Question. In which of the following pairs are both the ions coloured in aqueous solution?
(At. no. : Sc = 21, Ti = 22, Ni = 28, Cu = 29,Co = 27)
(a) Ni²⁺, Cu⁺
(b) Ni²⁺, Ti³⁺
(c) Sc³⁺, Ti³⁺
(d) Sc³⁺, Co²⁺ 
Answer. B

Question. Four successive members of the first row transition elements are listed below with their atomic numbers.Which one of them is expected to have the highest third ionisation enthalpy?
(a) Vanadium (Z = 23)
(b) Chromium (Z = 24)
(c) Manganese (Z = 25)
(d) Iron (Z = 26) 
Answer. C

Question. The aqueous solution containing which one of the following ions will be colourless?
(Atomic number : Sc = 21, Fe = 26,Ti = 22, Mn = 25)
(a) Sc³⁺
(b) Fe²⁺
(c) Ti³⁺
(d) Mn²⁺
Answer. A

Question. Which one of the following characteristics of the transition metals is associated with their catalytic activity?
(a) High enthalpy of atomization
(b) Paramagnetic behaviour
(c) Colour of hydrated ions
(d) Variable oxidation states
Answer. D

Question. The basic character of the transition metal monoxides follows the order
(Atomic no’s. Ti = 22, V = 23, Cr = 24, Fe = 26)
(a) VO > CrO > TiO > FeO
(b) CrO > VO > FeO > TiO
(c) TiO > FeO > VO > CrO
(d) TiO > VO > CrO > FeO
Answer. D

Question. Which of the following shows maximum number of oxidation states?
(a) Cr
(b) Fe
(c) Mn
(d) V 
Answer. C

Question. Which ion is colourless?
(a) Cr⁴⁺
(b) Sc³⁺
(c) Ti³⁺
(d) V³⁺ 
Answer. B

Question. Bell metal is an alloy of
(a) Cu + Zn
(b) Cu + Sn
(c) Cu + Pb
(d) Cu + Ni 
Answer. B

Question. In which of the following compounds transition metal has zero oxidation state?
(a) NOClO₄
(b) NH₂NH₂
(c) CrO₅
(d) [Fe(CO)₅] 
Answer. D

Question. Which one of the following ionic species will impart colour to an aqueous solution?
(a) Zn²⁺
(b) Cu⁺
(c) Ti⁴⁺
(d) Cr³⁺
Answer. D

Question. A transition element X has a configuration [Ar]3d⁴ in its +3 oxidation state. Its atomic number is
(a) 22
(b) 19
(c) 25
(d) 26 
Answer. C

Question. Amongst TiF₆^2–, CoF₆^3–, Cu₂Cl₂ and NiCl₄^2–, which are the colourless species? (Atomic number of Ti = 22, Co = 27, Cu = 29, Ni = 28)
(a) CoF₆^3– and NiCl₄^2–
(b) TiF₆^2– and Cu₂Cl₂
(c) Cu₂Cl₂ and NiCl₄^2–
(d) TiF₆^2– and CoF₆^3–
Answer. B

Question. The mercury is the only metal which is liquid at 0°C.
This is due to its
(a) high vapour pressure
(b) weak metallic bond
(c) high ionization energy
(d) both (b) and (c). 
Answer. D

Question. The manganate and permanganate ions are tetrahedral, due to
(a) the p-bonding involves overlap of d-orbitals of oxygen with d-orbitals of manganese
(b) the p-bonding involves overlap of p-orbitals of oxygen with d-orbitals of manganese
(c) there is no p-bonding
(d) the p-bonding involves overlap of p-orbitals of oxygen with p-orbitals of manganese.
Answer. B

Question. When neutral or faintly alkaline KMnO₄ is treated with potassium iodide, iodide ion is converted into ‘X’. ‘X’ is
(a) I₂
(b) IO₄^–
(c) IO₃^–
(d) IO^–
Answer. C

Question. Which one of the following ions exhibits d-d transition and paramagnetism as well?
(a) CrO₄^2–
(b) Cr₂O₇^2–
(c) MnO₄^–
(d) MnO₄^2– 
Answer. D

Question. Name the gas that can readily decolourise acidified KMnO₄ solution.
(a) SO₂
(b) NO₂
(c) P2O₅
(d) CO₂
Answer. A

Question. Which one of the following statements is correct when SO₂ is passed through acidified K₂Cr₂O₇ solution?
(a) SO₂ is reduced.
(b) Green Cr₂(SO₄)₃ is formed.
(c) The solution turns blue.
(d) The solution is decolourised. 
Answer. B

Question. Assuming complete ionisation, same moles of which of the following compounds will require the least amount of acidified KMnO₄ for complete oxidation?
(a) FeSO₃
(b) FeC₂O₄
(c) Fe(NO₂)₂
(d) FeSO₄ 
Answer. D

Question. The reaction of aqueous KMnO₄ with H₂O₂ in acidic conditions gives
(a) Mn⁴⁺ and O₂
(b) Mn²⁺ and O₂
(c) Mn²⁺ and O₃
(d) Mn⁴⁺ and MnO₂.
Answer. B

Question. Which of the statements is not true?
(a) On passing H₂S through acidified K₂Cr₂O₇ solution, a milky colour is observed.
(b) Na₂Cr₂O₇ is preferred over K₂Cr₂O₇ in volumetric analysis.
(c) K₂Cr₂O₇ solution in acidic medium is orange.
(d) K₂Cr₂O₇ solution becomes yellow on increasing the pH beyond 7.
Answer. B

Question. Acidified K₂Cr₂O₇ solution turns green when Na₂SO₃ is added to it. This is due to the formation of
(a) Cr₂(SO₄)₃
(b) CrO₄^2–
(c) Cr₂(SO₃)₃
(d) CrSO₄
Answer. A

Question. The number of moles of KMnO₄ reduced by one mole of KI in alkaline medium is
(a) one
(b) two
(c) five
(d) one fifth.
Answer. B

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