CBSE Class 12 Chemistry The d and f Block Elements MCQs Set I

CRITICAL THINKING TYPE QUESTIONS

Question. Which one of the following is an amphoteric oxide ?
(i) Mn₂O₇ (ii) CrO
(iii) V₂O₄ (iv) Cr₂O₃
(a) (i) and (ii)
(b) (ii), (iii) and (iv)
(c) (iii) and (iv)
(d) (ii) and (iv)

Answer: c

Question. Arrange the following increasing order of acidic character?
Mn₂O₇(A), Mn₂O₃(B), MnO(C)?
(a) C, A, B
(b) A,A, C, B
(c) B,  C
(d) C, B, A 

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 one of the following transition metal ions shows magnetic moment of 5.92 BM?
(a) Mn²⁺
(b) Ti³⁺
(c) Cr³⁺
(d) Cu²⁺

Answer: a

Question. When KMnO₄ solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time because
(a) CO₂ is formed as the product.
(b) reaction is exothermic.
(c) MnO₄^- catalyses the reaction.
(d) Mn²⁺ acts as autocatalyst. 

Answer: d

Question. For the ions Zn²⁺, Ni²⁺ and Cr³⁺ which among the following statements is correct?
(atomic number of Zn = 30, Ni = 28 and Cr = 24)
(a) All these are colourless
(b) All these are coloured
(c) Only Ni²⁺ is coloured and Zn²⁺ and Cr³⁺ are colourless
(d) Only Zn²⁺ is colourless and Ni²⁺ and Cr³⁺ are coloured

Answer: d

Question. In the following salts the lowest value of magnetic moment is observed in
(a) MnSO₄. 4H₂O
(b) CuSO₄.5H₂O
(c) FeSO₄.6H₂O
(d) ZnSO₄.7H₂O

Answer: a

Question. Cuprous ion is colourless while cupric ion is coloured because
(a) both have half filled p-and d-orbitals
(b) cuprous ion has incomplete d-orbital and cupric ion has a complete d-orbital
(c) both have unpaired electrons in the d-orbitals
(d) cuprous ion has complete d-orbital and cupric ion has an imcomplete d-orbita 

Answer: d

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. Knowing that the chemistry of lanthanoids(Ln) is dominated by its + 3 oxidation state, which of the following statements is incorrect?
(a) The ionic size of Ln (III) decrease in general with increasing atomic number
(b) Ln (III) compounds are generally colourless.
(c) Ln (III) hydroxide are mainly basic in character.
(d) Because of the large size of the Ln (III) ions the bonding in its compounds is predominantly ionic in character.

Answer: b

Question. The standard redox potentials for the reactions
Mn²⁺ + 2e^– → Mn and Mn³⁺ + e^– → Mn²⁺ are –1.18 V and 1.51 V respectively. What is the redox potential for the reaction Mn³⁺ + 3e^– →  Mn?
(a) 0.33 V
(b) 1.69 V
(c) – 0.28 V
(d) – 0.85 V

Answer: c

Question. Which of the following conversions can be carried out by both acidified K₂Cr₂O₄ and acidified KMnO₄?
(i) Fe²⁺ → Fe³⁺ + e–
(ii) I– →
(iii) I– → I₂
(iv) H₂S → S
(a) (i) and (iii)
(b) (ii) and (iv)
(c) (i), (iii) and (iv)
(d) (i), (ii) and (iii)

Answer: c

Question. The +3 ion of which one of the following has half filled 4f subshell?
(a) La
(b) Lu
(c) Gd
(d) Ac

Answer: c

Question. Identify the product and its colour when MnO₂ is fused with solid KOH in the presence of O₂.
(a) KMnO₄, purple
(b) K₂MnO₄, dark green
(c) MnO, colourless
(d) Mn₂O₃, brown

Answer: b

Question. When a small amount of KMnO₄ is added to concentrated H₂SO₄, a green oily compound is obtained which is highly explosive in nature. Compound may be
(a) MnSO₄
(b) Mn₂O₇
(c) MnO₂
(d) Mn₂O₃

Answer: b

Question. Which of the following arrangements does not represent the correct order of the property stated against it ?
(a) V²⁺ < Cr²⁺ < Mn²⁺ < Fe²⁺ : Paramagnetic behaviour
(b) Ni²⁺ < Co²⁺ < Fe²⁺ < Mn²⁺ : Ionic size
(c) Co³⁺ < Fe³⁺ < Cr³⁺ < Sc³⁺ : Stability in aqueous solution
(d) Sc < Ti < Cr < Mn : Number of oxidation states

Answer: a

Question. The electronic configuration of Cu(II) is 3d⁹ whereas that of Cu(I) is 3d¹⁰. Which of the following is correct ?
(a) Cu (II) is more stable
(b) Cu (II) is less stable
(c) Cu (I) and (II) are equally stable
(d) Stability of Cu (I) and Cu (II) depends on nature of copper salts 

Answer: a

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. Solution of oxalate is colourless. It is made acidic by adding excess of H⁺, then titrated with KMnO₄. Now at a moment if someone has added large amount of KMnO₄, in it then no. of possible products are
(a) CO₂, Mn²⁺, H₂O
(b) CO₂, MnO₂, H₂O
(c) MnO₂, H₂O, CO₂
(d) CO₂, MnO₂, H₂O, Mn²⁺ 

Answer: b

Question. Among the oxides, Mn₂O₇ (I), V₂O₃ (II), V₂O₅ (III), CrO
(IV) and Cr₂O₃ (V) the basic oxides are
(a) I and II
(b) II and III
(c) III and IV
(d) II and IV

Answer: d

Question. Dichromate [Cr(VI) ] is a strong oxidizing agent whereas Mo(VI) and W(VI) are found to be not. This is due to
(a) Lanthanoid contraction
(b) Down the group metallic character increases
(c) Down the group metallic character decreases
(d) Both (a) and (b) 

Answer: b

Question. The colour of the following ions V²⁺, V³⁺, V⁴⁺, Fe²⁺, Fe³⁺ are respectively
(a) green, violet, blue, green, yellow
(b) yellow, green, violet, green, blue
(c) violet, green, yellow, green, blue
(d) yellow, green, blue, green, violet

Answer: d

Question. Although + 3 is the characteristic oxidation state for lanthanoids but cerium also shows + 4 oxidation state because _________ .
(i) it has variable ionisation enthalpy
(ii) it has a tendency to attain noble gas configuration
(iii) it has a tendency to attain f ⁰ configuration
(iv) it resembles Pb⁴⁺
(a) (ii) and (iii)
(b) (i) and (iv)
(c) (ii) and (iv)
(d) (i), (ii) and (iii)

Answer: a

Question. Which of the following oxidising reaction of KMnO₄ occurs in acidic medium?
(i) Fe²⁺ (green) is converted to Fe³⁺ (yellow).
(ii) Iodide is converted to iodate.
(iii) Thiosulphate oxidised to sulphate.
(iv) Nitrite is oxidised to nitrate.
(a) (i) and (iii)
(b) (i) and (iv)
(c) (iv) only
(d) (ii) and (iv) 

Answer: b

Question. Four successive members of the first series of the transition metals are listed below. For which one of them the standard potential  Eº_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

MATCHING TYPE QUESTIONS

Question. Match the columns
Column-I                                             Column-II
(A) Compound formed when               (p) acidified
yellow CrO₄^2- is acidified.                       MnO₄^-
(B) reagent oxidises Fe²⁺ to Fe³⁺      (q) Cr₂O₇^2-
(C) Compound produced when         (r) K₂MnO₄
MnO₂ is fused with KNO₃
(D) Compound having dark               (s) KMnO₄
purple crystals isostructural
with KClO₄
(a) A – (q),B – (p), C – (r), D – (s)
(a) A – (p),B – (q), C – (r), D – (s)
(a) A – (q),B – (r), C – (p), D – (s)
(a) A – (q),B – (p), C – (s), D – (r)

Answer: a

Question. Match the columns
Column-I                     Column-II
(Ion)                           (Mcalculated)
(A) Ti²⁺                       (p) 2.84
(B) Zn²⁺                      (q) 5.92
(C) Mn²⁺                    (r) 0
(D) Sc³⁺                     (s) 4.90
(a) A – (s), B – (p), C – (q), D – (r).
(b) A – (r), B – (p), C – (q), D – (s).
(c) A – (p), B – (r), C – (q), D – (s).
(d) A – (p), B – (s), C – (q), D – (r).

Answer: c

Question. Match the columns
Column-I                                           Column-II
(A) Lanthanide hard as steel.               (p) Lu
(B) Lanthanide with maximum             (q) Tb
paramagnetic character in 
Ln⁴⁺ state. 
(C) Latnhanide with maximum            (r) Sm
value of E° for reaction
Ln³⁺(aq)+3e^– → Ln(s).
(D) Lanthanide whose Ln³⁺ ion is       (s) Eu
diamagnetic in nature
(a) A – (r), B – (s), C – (p), D – (q)
(b) A – (r), B – (q), C – (s), D – (p)
(c) A – (s), B – (r), C – (q), D – (p)
(d) A – (r), B – (s), C – (q), D – (p)

Answer: a

Question. Match the columns
Column-I                                              Column -II
(A) Metal of the 3d-series which            (p) Manganese
does not form MO type oxide.
(B) Metal of the 3d-series which           (q) Vanadium
forms most covalent oxide.
(C) Metal of the 3d-series which           (r) Scandium
forms the amphoteric oxide.
(a) A – (p), B – (r), C – (q)
(b) A – (r), B – (p), C – (q)
(c) A – (r), B – (q), C – (p)
(d) A – (q), B – (p), C – (r)

Answer: b

ASSERTION-REASON TYPE QUESTIONS

Directions : Each of these questions contain two statements,
Assertion and Reason. Each of these questions also has four alternative choices, only one of which is the correct answer. You have to select one of the codes (a), (b), (c) and (d) given below.
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion.
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct.

Question. Assertion : Magnetic moment values of actinides are lesser than the theoretically predicted values.
Reason : Actinide elements are strongly paramagnetic.

Answer: b

Question. Assertion : Cuprous ion (Cu⁺) has unpaired electrons while cupric ion (Cu⁺⁺) does not.
Reason : Cuprous ion (Cu⁺) is colourless whereas cupric ion (Cu⁺⁺) is blue in the aqueous solution

Answer: d

Question. Assertion : Transition metals are good catalysts.
Reason : V₂O₅ or Pt is used in the preparation of H₂SO₄ by contact process.

Answer: b

Question. Assertion : Transition metals show variable valency.
Reason : Transition metals have a large energy difference between the ns² and (n – 1)d electrons.

Answer: c