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

Question. For Zn²⁺, Ni²⁺, Cu²⁺ and Cr²⁺ which of the following statements is correct?
(a) Only Zn²⁺ is colourless and Ni²⁺, Cu²⁺ and Cr²⁺ are coloured.
(b) All the ions are coloured.
(c) All the ions are colourless.
(d) Zn²⁺ and Cu²⁺ are colourless while Ni²⁺ and Cr²⁺ are coloured.
Answer: a

Question. The equation 3MnO₄^2– + 4H⁺ → 2MnO₄^– + MnO₂ + 2H₂O represents
(a) reduction
(b) disproportionation
(c) oxidation in acidic medium
(d) reduction in acidic medium. 
Answer: b

Question. Which of the following statements is not correct about magnetic behaviour of substances?
(a) Diamagnetic substances are repelled by an applied magnetic field.
(b) Paramagnetic substances are attracted by an applied magnetic field.
(c) Magnetic moment of n unpaired electrons is given by μ = n(n − 2) B.M.
(d) Magnetic moment increases as the number of unpaired electrons increases.
Answer: c

Question. Identify the species in which the metal atom is in +6 oxidation state.
(a) MnO₄^–
(b) Cr(CN)₆^3–
(c) NiF₆^2–
(d) CrO₂Cl₂
Answer: d

Question. Which of the following compounds is expected to be coloured?
(a) Ag₂SO₄
(b) CuF₂
(c) MgF₂
(d) CuCl
Answer: b

Question. Transition metals make the most efficient catalysts because of their ability to
(a) adopt multiple oxidation states and to form complexes
(b) form coloured ions
(c) show paramagnetism due to unpaired electrons
(d) form a large number of oxides.
Answer: a

Question. The correct order of ionic radii of Ce, La, Pm and Yb in +3 oxidation state is
(a) La³⁺ < Pm³⁺ < Ce³⁺ < Yb³⁺
(b) Yb³⁺ < Pm³⁺ < Ce³⁺ < La³⁺
(c) La³⁺ < Ce³⁺ < Pm³⁺ < Yb³⁺
(d) Yb³⁺ < Ce³⁺ < Pm³⁺ < La³⁺
Answer: b

Question. Following order is observed in oxidising power of certain ions:
VO₂⁺ < Cr₂O₇^2– < MnO₄^–
The reason for this increasing order of oxidising power is
(a) increasing stability of the lower species to which they are reduced
(b) increasing stability of the higher species to which they are oxidised
(c) increasing stability of the higher species to which they are reduced
(d) increasing stability of the lower species to which they are oxidised.
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 Cu(II) are equally stable.
(d) Stability of Cu(I) and Cu(II) depends on nature of copper salts.
Answer: a

 Question. Highest oxidation state of manganese in fluoride is +4 (MnF₄) but highest oxidation state in oxides is +7 (Mn₂O₇) because
(a) fluorine is more electronegative than oxygen
(b) fluorine does not possess d-orbitals
(c) fluorine stabilises lower oxidation state
(d) in covalent compounds, fluorine can form single bond only while oxygen forms double bond.
Answer: d

Question. Which of the following compounds is not coloured?
(a) Na₂[CuCl₄]
(b) Na₂[CdCl₄]
(c) K₄[Fe(CN)]₆]
(d) K₃[Fe(CN)₆]
Answer: b

Question. Which is the non-lanthanide element?
(a) La
(b) Lu
(c) Pr
(d) Pm
Answer: a

Question. CuSO₄ is paramagnetic while ZnSO₄ is diamagnetic because
(a) Cu²⁺ ion has 3d⁹ configuration while Zn²⁺ ion has 3d¹⁰ configuration
(b) Cu²⁺ ion has 3d⁵ configuration while Zn²⁺ ion has 3d⁶ configuration
(c) Cu²⁺ has half filled orbitals while Zn²⁺ has fully filled orbitals
(d) CuSO₄ is blue in colour while ZnSO₄ is white.
Answer: a

Question. Cu⁺ ion is not stable in aqueous solution because
(a) second ionisation enthalpy of copper is less than the first ionisation enthalpy
(b) large value of second ionisation enthalpy of copper is compensated by much more negative hydration energy of Cu²⁺_(aq)
(c) hydration energy of Cu⁺_(aq) is much more negative than that of Cu²⁺_(aq)
(d) many copper (I) compounds are unstable in aqueous solution and undergo disproportionation reaction.
Answer: b

Question. For the given reactions :
[Fe(H₂O)₆]²⁺ + NO₃^– + H⁺ → X + Y + H₂O
[Fe(H2O)₆]²⁺ + X → Z + H₂O
The incorrect statement about X, Y and Z is
(a) Magnetic moment of Y is 5.9 B.M.
(b) Oxidation state of Fe in Z is +1.
(c) Complex Z is reddish-brown in colour.
(d) X is an acidic oxide of nitrogen.
Answer: d

Question. Transition elements form binary compounds with halogens. Which of the following elements will form MF₃ type compounds?
(a) Cr
(b) Cu
(c) Ni
(d) All of these
Answer: a

Question. Which of the following catalysts is not correctly matched with the reaction?
(a) Vanadium(V) oxide in contact process for oxidation of SO₂ to SO₃.
(b) Finely divided iron in Haber’s process in conversion of N₂ and H₂ to NH₃.
(c) PtCl₂ catalyses the oxidation of ethyne to ethanal in the Wacker process.
(d) Ni in presence of hydrogen for conversion of vegetable oil to ghee.
Answer: c

Question. Select the correct option, among Sc(III),Ti(IV), Pd(II) and Cu(II) ions,
(a) all are paramagnetic
(b) all are diamagnetic
(c) Sc(III), Ti(IV) are paramagnetic and Pd(II),Cu(II) are diamagnetic
(d) Sc(III), Ti(IV) are diamagnetic and Pd(II),Cu(II) are paramagnetic.
Answer: d

 Question. EMn3+/Mn2+ is highly positive than that of E°Cr3+/Cr2+ or E°Fe3+/Fe2+ because
(a) Mn2+ (d5) can be easily oxidised to Mn3+(d4) due to low ionisation enthalpy
(b) third ionisation enthalpy of Mn is much larger due to stable half filled d5 electronic configuration of Mn2+
(c) Mn3+ is more stable than Mn2+ due to higher oxidation state.
(d) second ionisation enthalpy of Mn is higher than third ionisation enthalpy.
Answer: b

Question. Interstitial compounds are nonstoichiometric compounds formed by trapping small atoms like C, H or N in crystal lattices of transition metals. Which of the following properties is not shown by these compounds?
(a) They have high melting points, higher than those of pure metals.
(b) They are very hard, some borides are comparable to diamond in hardness.
(c) They are chemically very reactive.
(d) They retain metallic conductivity.
Answer: c

Question. Arrange the oxides of manganese according to increasing acidic strength.
(a) MnO < Mn₃O₄ < Mn₂O₃ < MnO₂ < Mn₂O₇
(b) Mn₂O₇ < MnO₂ < Mn₂O₃ < Mn₃O₄ < MnO
(c) MnO₂ < Mn₂O₇ < Mn₃O₄ < Mn₂O₃ < MnO
(d) Mn₃O₄ < Mn₂O₃ < Mn₂O₇ < MnO₂ < MnO
Answer: a

Question. The magnetic moment of a divalent ion in aqueous solution with atomic number 25 is
(a) 5.9 B.M
(b) 2.9 B.M
(c) 6.9 B.M
(d) 9.9 B.M. 
Answer: a

Question. Which of the following statement 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. Which of the following transition metal ions is colourless?
(a) V²⁺
(b) Cr³⁺
(c) Zn²⁺
(d) Ti³⁺
Answer: c

Question. Most of the transition metals exhibit
(i) paramagnetic behaviour
(ii) diamagnetic behaviour
(iii) variable oxidation states
(iv) formation of coloured ions
(a) (ii), (iii) and (iv)
(b) (i), (iii) and (iv)
(c) (i), (ii) and (iii)
(d) (i), (ii) and (iv)
Answer: b

Question. Few electrode potential values are given below:
Cr³⁺/Cr²⁺ = – 0.41 V
Cr²⁺/Cr = – 0.90 V
Mn³⁺/Mn²⁺ = +1.57 V
Mn^2+/Mn = –1.18 V
On the basis of these values, Krish concluded the following statements:
I. Cr²⁺ is a reducing agent
II. Mn³⁺ is an oxidizing agent
III. both Cr²⁺ and Mn³⁺ exhibit d⁴ electronic configuration
IV. when Cr²⁺ is used as a reducing agent, the chromium ion attains d⁵ electronic configuration.
The incorrect conclusion made by him is
(a) I
(b) II
(c) III
(d) IV
Answer: d

Question. Consider the following statements
I. La(OH)₃ is least basic among hydroxides of lanthanides.
II. Zr⁴⁺ and Hf ⁴⁺ possess almost the same ionic radii.
III. Ce⁴⁺ can act as an oxidizing agent.
Which of the above is/are true?
(a) I and III
(b) II and III
(c) II only
(d) I and II
Answer: b

Case Based MCQs

Case I : Read the passage given below and answer the following questions.

Transition metal oxides are compounds formed by the reaction of metals with oxygen at high temperature. The highest oxidation number in the oxides coincides with the group number. In vanadium, there is a gradual change from the basic V₂O₃ to less basic V₂O₄ and to amphoteric V₂O₅⋅ V₂O₄ dissolves in acids to give VO²⁺ salts. Transition metal oxides are commonly utilized for their catalytic activity and semiconductive properties. Transition metal oxides are also frequently used as pigments in paints and plastic. Most notably titanium dioxide. One of the earliest application of transition metal oxides to chemical industry involved the use of vanadium oxide for catalytic oxidation of sulfur dioxide to sulphuric acid. Since then, many other applications have emerged, which include benzene oxidation to maleic anhydride on vandium oxides; cyclohexane oxidation to adipic acid on cobalt oxides. An important property of the catalyst material used in these processes is the ability of transition metals to change their oxidation state under a given chemical potential of reductants and oxidants.

Question. Which of the following statements is false?
(a) With fluorine vanadium can form VF₅.
(b) With chlorine vanadium can form VCl₅.
(c) Vanadium exhibits highest oxidation state in oxohalides VOCl₃, VOBr₃ and fluoride VF₅.
(d) With iodine vanadium cannot form VI₅ due to oxidising power of V⁵⁺ and reducing nature of I^–.
Answer: b

Question. Vanadyl ion is
(a) VO²⁺
(b) VO²⁺
(c) V₂O⁺
(d) VO₄^3–
Answer: a

Question. Which oxide of vanadium is most likely to be basic and ionic ?
(a) VO
(b) V₂O₃
(c) VO₂
(d) V₂O₅
Answer: a

Question. Identify the oxidising agent in the following reaction.
V₂O₅ + 5Ca → 2V + 5CaO
(a) V₂O₅
(b) Ca
(c) V
(d) None of these
Answer: a

Question. The oxidation state of vanadium in V₂O₅ is
(a) +5/2
(b) +7
(c) +5
(d) +6
Answer: c

Case II : Read the passage given below and answer the following questions.

The lanthanide series is a unique class of 15 elements with relatively similar chemical properties. They have atomic number ranging from 57 to 71, which corresponds to the filling of the 4f orbitals with 14 electrons. This configuration leads to phenomenon known as lanthanide contraction. The lanthanides are sometimes referred to as the ‘rare earth elements’, leading to misconception that they are rare. In fact many of the rare earth elements are more common than gold, silver and in some cases, lead. The lanthanides are commonly found in nature as a mixture in a number of monazite (LnPO₄) and bastnaesite (LnCO₃F) in the +3 oxidation state.

The chemical and physical properties of lanthanides provide the unique features that set them apart from other elements. Lanthanides are most stable in the +3 oxidation state. Yb and Sm though stable in the +3 state, also have accessible +2 oxidation states. The ease of accessibility of both oxidation states is quite important in chemical synthesis and these elements act as Lewis acid in the +3 oxidation state and single electron reductant in the +2 oxidation state.

In the following questions , a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices on the basis of the above passage.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.

Question. Assertion : The elements scandium and yttrium are called “rare earths”.
Reason : Scandium and yttrium are rare on earth’s crust.
Answer: c

Question. Assertion : All lanthanides have similar chemical properties.
Reason : Because the lanthanoids differ only in the number of 4f – electrons.
Answer: a

Question. Assertion : There is continuous increase in size among lanthanides.
Reason : Lanthanides show lanthanide contraction.
Answer: d

Question. Assertion : Separation of lanthanide elements is difficult.
Reason : They have similar chemical properties.
Answer: a

Question. Assertion : Yb²⁺ is more stable than Yb³⁺.
Reason : Electronic configuration of Yb²⁺ is [Xe]₄f ⁷.
Answer: c

Case III : Read the passage given below and answer the following questions.

The transition elements have incompletely filled d-subshells in their ground state or in any of their oxidation states. The transition elements occupy position in between s- and p-blocks in groups 3-12 of the Periodic table. Starting from fourth period, transition elements consists of four complete series : Sc to Zn, Y to Cd and La, Hf to Hg and Ac, Rf to Cn. In general, the electronic configuration of outer orbitals of these elements is (n – 1)d^1–10 ns^0–2. The electronic configurations of outer orbitals of Zn, Cd, Hg and Cn are represented by the general formula (n – 1)d¹⁰ ns². All the transition elements have typical metallic properties such as high tensile strength, ductility, malleability. Except mercury, which is liquid at room temperature, other transition elements have typical metallic structures. The transition metals and their compounds also exhibit catalytic property and paramagnetic behaviour. Transition metal also forms alloys. An alloy is a blend of metals prepared by mixing the components. Alloys may be homogeneous solid solutions in which the atoms of one metal are distributed randomly among the atoms of the other.

Question. The electronic configuration of tantalum (Ta) is
(a) [Xe]4f⁰ 5d ¹ 6s²
(b) [Xe]4f¹⁴ 5d² 6s²
(c) [Xe]4f ¹⁴ 5d ³ 6s²
(d) [Xe]4f ¹⁴ 5d⁴ 6s²
Answer: c

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

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

Question. Transition elements form alloys easily because they have
(a) same atomic number
(b) same electronic configuration
(c) nearly same atomic size
(d) same oxidation states.
Answer: c

Question. The correct statement(s) among the following is/are
(i) all d- and f-block elements are metals
(ii) all d- and f-block elements form coloured ions
(iii) all d- and f-block elements are paramagnetic.
(a) (i) only
(b) (i) and (ii) only
(c) (ii) and (iii) only
(d) (i), (ii) and (iii)
Answer: a

Case IV : Read the passage given below and answer the following questions.

The unique behaviour of Cu, having a positive E° accounts for its inability to liberate H₂ from acids. Only oxidising acids (nitric and hot concentrated sulphuric acid) react with Cu, the acids being reduced. The stability of the halffilled (d⁵) subshell in Mn²⁺ and the completely filled (d¹⁰) configuration in Zn²⁺ are related to their E°_{(M³⁺/M²⁺)} values. The low value for Sc reflects the stability of Sc³⁺ which has a noble gas configuration. The comparatively high value for Mn shows that Mn²⁺(d⁵) is particularly stable, whereas a comparatively low value for Fe shows the extra stability of Fe³⁺(d⁵). The comparatively low value for V is related to the stability of V²⁺ (half-filled t_2g level).

Question. E° values for the couples Cr³⁺/Cr²⁺ and Mn³⁺/Mn²⁺ are –0.41 and +1.51 volts respectively.
These values suggest that
(a) Cr²⁺ acts as a reducing agent whereas Mn3+ acts as an oxidizing agent
(b) Cr²⁺ is more stable than Cr³⁺ state
(c) Mn³⁺ is more stable than Mn²⁺
(d) Cr²⁺ acts as an oxidizing agent whereas Mn³⁺ acts as a reducing agent.
Answer: a

Question. The stability of Cu²⁺_(aq) rather than Cu⁺_(aq) is due to
(a) more negative Δ_hyd H° of Cu²⁺_(aq)
(b) less negative Δ_hyd H° of Cu²⁺_(aq)
(c) more positive Δ_hyd H° of Cu²⁺_(aq)
(d) less positive Δ_hyd H° of Cu²⁺_(aq)
Answer: a

Question. The reduction potential values of M, N and O are +2.46, –1.13 and –3.13 V respectively.Which of the following order is correct regarding their reducing property?
(a) O > N > M
(b) O > M > N
(c) M > N > O
(d) M > O > N
Answer: a

Question. Standard reduction electrode potential of Zn²⁺/Zn is – 0.76 V. This means
(a) ZnO cannot be reduced to Zn by H₂ under standard conditions
(b) Zn cannot liberate H₂ with concentrated acids
(c) Zn is generally the anode in an electrochemical cell
(d) Zn is generally the cathode in an electrochemical cell.
Answer: a

Question. Which of the following statements are true?
(I) Mn²⁺ compounds are more stable than Fe²⁺ towards oxidation to +3 state.
(II) Titanium and copper both in the first series of transition metals exhibits +1 oxidation state most frequently.
(III) Cu+ ion is stable in aqueous solutions.
(IV) The E° value for the Mn³⁺/Mn²⁺ couple is much more positive than that for Cr³⁺/Cr²⁺ or Fe³⁺/Fe²⁺.
(a) (II) and (III)
(b) (I) and (IV)
(c) (I) and (III)
(d) (II) and (IV)
Answer: b

Case V : Read the passage given below and answer the following questions.

The f-block elements are those in which the differentiating electron enters the (n –2)f orbital. There are two series of f-block elements corresponding to filling of 4f and 5f-orbitals. The series of 4f-orbitals is called lanthanides. Lanthanides show different oxidation states depending upon stability of f ⁰, f ⁷ and f ¹⁴ configurations, though the most common oxidation states is +3. There is a regular decrease in size of lanthanides ions with increase in atomic number which is known as lanthanide contraction.

Question. Lanthanide contraction is observed in
(a) Gd
(b) At
(c) Xe
(d) Te
Answer: a

Question. Identify the incorrect statement among the following.
(a) Lanthanoid contraction is the accumulation of successive shrinkages.
(b) The different radii of Zr and Hf is due to consequence of the lanthanoid contraction.
(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. Which of the following is not the configuration of lanthanoid?
(a) [Xe]4f¹⁰6s²
(b) [Xe]4f¹⁵d¹⁶s²
(c) [Xe]4d¹⁴5d¹⁰6s²
(d) [Xe]4f⁷⁵d¹⁶s²
Answer: c

Question. The atomic numbers of three lanthanide elements X, Y and Z are 65, 68 and 70 respectively,their Ln³⁺ electronic configuration is
(a) 4f ⁸, 4f ¹¹, 4f¹³
(b) 4f ¹¹, 4f ⁸, 4f ¹³
(c) 4f ⁰, 4f ², 4f¹¹
(d) 4f ³, 4f ⁷, 4f ⁹
Answer: a

Question. Name a member of the lanthanoid series which is well known to exhibit +4 oxidation state.
(a) Cerium (Z = 58)
(b) Europium (Z = 63)
(c) Lanthanum (Z = 57)
(d) Gadolinium (Z = 64)
Answer: a