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The d-and f-Block Elements Class 12 Chemistry MCQs Pdf
1. In which of the following pairs, both the ions are coloured in aqueous solutions?
(a) Sc3+, Ti
(b) Sc3+, Co2+
(c) Ni2+, Cu+
(d) Ni2+, Ti3+
[Atomic no of Sc = 21, Ti = 22, Ni = 28, Co = 27, Cu = 29]
Answer/Explanation
Answer: d
Explaination:
(d) Ni2+, Ti3+ are coloured due to presence of unpaired electrons.
2. Which of the following is most stable in aqueous solution?
(a) Mn2+
(b) Cr3+
(c) V3+
(d) Ti3+
Answer/Explanation
Answer: b
Explaination:
(b) Cr3+
∵ t2g3+ (half filled p-orbitals) are more stable.
3. The number of moles of KMnO. that will be needed to react with one mole of SO32- in acidic solution.
(a) 1
(b) 3/5
(c) 4/5
(d) 2/5
Answer/Explanation
Answer: d
Explaination:
(d) 2 MnO4– + 5SO32 + 16H+ → 2Mn2+ + 5SO42+ + 8H20
5 moles of SO32- needs 2 moles of KMnO4
1 mole of SO32- needs 2/5 moles of KMnO4
4. The correct order of decreasing second ionisation enthalpy of Ti(22), V(23), Cr(24) Mn(25)
(a) V > Mn > Cr > Ti
(b) Mn > Cr > Ti > V
(c) Ti > V > Cr > Mn
(d) Cr > Mn > V > Ti
Answer/Explanation
Answer: d
Explaination:
(d) ∵ Cr+ (4s°3d5), Mn+ 4s13d5, V1(4s+3d3), Ti+4s13d2
5. Which of the following pairs has the same ionic size?
(a) Zr4+, Hf4+
(b) Zn2+, Hf4+
(c) Fe2+, Ni2+
(d) Zr4+, Ti4+
Answer/Explanation
Answer: a
Explaination:
(a) Zr4+, Hf have similar size due to lanthanoid contraction.
6. Acidified K2Cr207 solution turns green when S02 gas is passed through it due to formation of
(a) Cr2(SO4)3
(b) CrO42-
(c) Cr2(SO3)3
(d) CrSO4
Answer/Explanation
Answer: a
Explaination: (a) It is due to formation of chromium sulphate.
7. The stability of Mn2+, Fe2+, Cr2+, Co2+ is in order of (At No. of Mn = 25, Fe = 26, Cr = 24, Co = 27)
(a) Mn2+ > Fe2+ > Cr2+ > Co2+
(b) Fe2+ > Mn2+ > Co2+ > Cr2+
(c) Co2+ > Mn2+ > Fe2+ > Cr2+
(d) Cr2+ > Mn2+ > Co2+ > Fe2+
Answer/Explanation
Answer: a
Explaination:
(a) Mn2+ (3d5) is most stable, Fe2+ (3d6), Cr2+(3d4 Co2+(3d1)
8. Which of the following does not give 02 on heating?
(a) K2Cr2O7
(b) (NH4)2 Cr2O7
(c) KClO3
(d) Zn(ClO3)2
Answer/Explanation
Answer:
Explaination:
9. Which of the following lanthanoid ion is diamagnetic? (At No. of Ce = 58, Sm = 62, Eu = 63 Yb = 70)
(a) Eu2+
(b) Yb2+
(c) Ce2+
(d) Sm2+
Answer/Explanation
Answer: b
Explaination:
(b) Yb2+ (4f14) does not have unpaired election, therefore, diamagnetic.
10. The reaction of acidified KMnO. and FLO, gives
(a) Mn4+ and O2
(b) Mn2+ and O2
(c) Mn2+ and O3
(d) Mn4+ and MnO2
Answer/Explanation
Answer: b
Explaination:
(b) 2MnO4 + 6H4 + 5H2O2 → 2Mn2+ + 8H2O + 5O2
11. Magnetic moment of 2.83 BM is given by which of the following ion?
(a) Ti3+
(b) Ni2+
(c) Cr3+
(d) Mn2+
Answer/Explanation
Answer: b
Explaination:
(b) Ni2+ has 2 unpaired electrons.
12. The colour of KmnO, is due to
(a) L → M charge transfer transition
(b) a → σ* transition
(c) M → L charge transfer transition
(d) d → d transition.
Answer/Explanation
Answer:
Explaination:
(a) It is due to L → M charge transfer transition by absorbing light from visible region and radiates purple colour.
13. KMnO4 is not acidified by HCl instead of H2SO4 because
(a) H2 SO4 is stronger acid than HCl
(b) HCl is oxidised to Cl2 by KMnO4
(c) H2SO4 is dibasic acid
(d) rate is faster in presence of H2SO4
Answer/Explanation
Answer: b
Explaination:
(b) 2KMnO4 + 16 HCl → 2KCl + 2MnCl2 + 5Cl2 + 2H2O
14. Out of Mn2O7 V2O3, V2O5, CrO, Cr2O3, the basic oxides are
(a) Mn2O7, V2O3
(b) V2O3, V2O5
(c) V2O5, CrO
(d) V2O3 and CrO
Answer/Explanation
Answer: d
Explaination:
(d) V2O3 and CrO are basic oxides due to lower, oxidation states.
15. The oxidation state of Cr in final product formed by reaction of KI and acidified dichromate solution is
(a) +4
(b) +6
(c) +2
(d) +3
Answer/Explanation
Answer: d
Explaination:
(d) Cr3+ is formed.
16. KMnO4 gets reduced to
(a) K2MnO4 in neutral medium
(b) MnO2 in acidic medium
(c) Mn2+ in alkaline medium
(d) MnO2 in neutral medium
Answer/Explanation
Answer:
Explaination:
17. The electronic configuration of Cu(II) is 3d9 whereas that of Cu(I) is 3d10. Which of the following is correct? [NCERT Exemplar]
(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/Explanation
Answer: a
Explaination:
(a) Cu(II) is more stable due to higher hydration energy.
18. Metallic radii of some transition elements are given below. Which of these elements will have highest density? [NCERT Exemplar]
(a) Fe
(b) Ni
(c) Co
(d) Cu
Answer/Explanation
Answer: d
Explaination:
(d) Cu has highest density due to greater atomic mass.
19. Generally transition elements form coloured salts due to the presence of unpaired electrons. Which of the following compounds will be coloured in solid state?
(NCERT Exemplar]
(a) Ag2SO4
(b) CuF2
(c) ZnF2
(d) Cu2Cl2
Answer/Explanation
Answer: b
Explaination:
(b) CUF2 is coloured due to presence ofunpaired electron in d-orbital.
20. On addition of small amount of KMnO4 to concentrated H2SO4, a green oily compound is obtained which is highly explosive in nature. Identify the compound from the following. [NCERT Exemplar]
(a) Mn2O7
(b) MnO2
(c) MnSO4
(c) Mn2O3
Answer/Explanation
Answer: a
Explaination:
(a) It is due to formation of Mn2O7.
21. Which of the following reactions are dispro-portionation reactions? [NCERT Exemplar]
(a) (i), (ii)
(b) (i), (ii), (iii)
(c) (ii), (iii)
(iv) (d) (i), (iv)
Answer/Explanation
Answer: b
Explaination:
(b) (i), (ii), (iii) are disproportionation because same substance is oxidised as well as reduced.
22. When KMnO. solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time because [NCERT Exemplar]
(a) CO2 is formed as the product.
(b) Reaction is exothermic.
(c) MnO4– catalyses the reaction.
(d) Mn2+ acts as autocatalyst.
Answer/Explanation
Answer: d
Explaination:
(d) Mn2+ acts as autocatalyst.
23. Anomalous electronic configuration in the 3d series are of
(a) Cr and Fe
(b) Cu and Zn
(c) Fe and Cu
(d) Cr and Cu
Answer
Answer: d
24. Which of the following are d-block elements but not regarded as transistion elements?
(a) Cu, Ag, Au
(b) Zn, Cd, Hg
(c) Fe, Co, Ni
(d) Ru, Rh, Pd
Answer
Answer: b
25. CuSO4. 5H2O is blue is colour because
(a) It contains water of crystallization.
(b) SO42- ions absorb red light.
(c) Cu2+ ions absorb orange red light.
(d) Cu2+ ions absorb all colours except red from the white light.
Answer
Answer: c
26. Transistion elements form alloys easily because they have
(a) Same atomic number
(b) Same electronic configuration
(c) Nearly same atomic size
(d) None of the above
Answer
Answer: c
27. Which one of the following characteristics of the transistion metals is associated with higher catalytic activity?
(a) High enthalpy of atomisation
(b) Paramagnetic behaviour
(c) Colour of hydrate ions
(d) Variable oxidation states
Answer
Answer: d
28. Which of the following has the maximum number of unpaired electrons?
(a) Mg2+
(b) Ti3+
(c) V3+
(d) Fe2+
Answer
Answer: d
29. The property which is not characteristic of transistion metals is
(a) variable oxidation states.
(b) tendency to form complexes.
(c) formation of coloured compounds.
(d) natural radioactivity.
Answer
Answer: d
30. Which of the following is incorrect for KMnO4 to be used as an oxidising agent?
(a) HCl cannot be used because some KMnO4 is consumed in the reaction.
(b) Nitric acid is not used for the above purpose because it itself acts as a self oxidising agent and will react with the reducing agent.
(c) The equivalent weight of KMnO4 in basic medium is 158.
(d) The number of electrons involved in oxidation of KMnO4 in acidic medium is 3.
Answer
Answer: d
31. Transistion metals, despite high E° oxidation, are poor reducing agents. The incorrect reason is
(a) high heat of vaporization.
(b) high ionization energies.
(c) low heats of hydration.
(d) complex forming nature.
Answer
Answer: d
32. Which of the following has magnetic moment value of 5.9?
(a) Fe2+
(b) Fe3+
(c) Ni2+
(d) Cu2+
Answer
Answer: b
Note: In the following questions two or more options may be correct. (Q.23 to Q.26)
33. In the form of dichromate, Cr (VI) is a strong oxidising agent in acidic medium but Mo (VI) in Mo03 and W (VI) in W03 are not because . [NCERT Exemplar]
(a) Cr (VI) is more stable than Mo(VI) and W(VI).
(b) Mo( VI) and W( VI) are more stable than Cr(VI).
(c) Higher oxidation states of heavier members of group-6 of transition series are more stable.
(d) Lower oxidation states of heavier *> members of group-6 of transition series are more stable.
Answer/Explanation
Answer:
Explaination:
(b) and (c) higher oxidation states are more stable.
34. Which of the following actinoids show oxidation states upto +7? [NCERT Exemplar]
(a) Am
(b) Pu
(c) U
(d) Np
Answer/Explanation
Answer:
Explaination:
(b) and (d) Pu and Np show oxidation state upto +7.
35. General electronic configuration of actionoids is (n – 2)f1 – 14 (n – 1)d0 – 2 ns².Which of the following actinoids have one electron in 6d orbital? [NCERT Exemplar]
(a) U (Atomic no. 92)
(b) Np (Atomic no. 93)
(c) Pu (Atomic no. 94)
(d) Am (Atomic no. 95)
Answer/Explanation
Answer:
Explaination:
(a) and (b) U and Np, U (5f36d17s2), Np (5f46d17S2)
36. Which of the following lanthanoids show +2 oxidation state besides the characteristic oxidation state +3 of lanthanoids? [NCERT Exemplar]
(a) Ce
(b) Eu
(c) Yb
(d) Ho.
Answer/Explanation
Answer:
Explaination:
(b) and (c) Eu2+ (4f7) and Yb2+ (4f14) are more stable.
37. Match the catalysts given in Column I with the processes given in Column II. [NCERT Exemplar]
Answer/Explanation
Answer:
Explaination:
(a) (iii)
(b) (iv)
(c) (ii)
(d) (v)
(e) (i)
38. Match the compounds/elements given in Column I with uses given in Column II.
Answer/Explanation
Answer:
Explaination:
(a) (ii)
(b) (i)
(c) (iv)
(d) (v)
(e) (iii)
39. Match the properties given in Column I with the metals given in Column II. [NCERT Exemplar]
Answer/Explanation
Answer:
Explaination:
(a) (iii)
(b) (i)
(c) (ii) Cr due to maximum number of unpaired electrons.
40. Match the statements given in Column I with the oxidation states given in Column II. [NCERT Exemplar]
Answer/Explanation
Answer:
Explaination:
(a) (iii)
(b) (i)
(c) (v)
(d) (ii)
41. 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.bvg
(a) Both assertion and reason are true, and reason is the correct explanation of the assertion.
(b) Both assertion and reason are true but reason is not the correct explanation of assertion.
(c) Assertion is not true but reason is true.
(d) Both assertion and reason are false. Assertion: Cu2+ iodide is not known.
Reason: Cu2+ oxidises I- to iodine.
Answer/Explanation
Answer: a
Explaination:
(a) Both assertion and reason are true, and reason is the correct explanation of the assertion.
Cu2+ 2I– → 2Cu+ +I2
42.
Answer/Explanation
Answer:
Explaination: 10CO2
43. Cr2O72- + 14H+ + 6Isup>- → 2Cr3++ ____ +7H2O
Answer/Explanation
Answer:
Explaination: 3I2
44. Cr2O72-+ 14H+ + 6Fe2+ → 2Cr3+ + ______ + 7H2O
Answer/Explanation
Answer:
Explaination: 6Fe3+
45. Cu2+ is reduced by CN– to Cu+ which forms the complex [Cu(CN)4]3-. [True/False]
Answer/Explanation
Answer:
Explaination: True.
46. The number of moles of Mohr’s salt required per mole of dichromate ion are 6. [True/False]
Answer/Explanation
Answer:
Explaination: True.
47. The colour of light absorbed by an aqueous solution of CuSO4 is orange red. [True/False]
Answer/Explanation
Answer:
Explaination: True.
48. There is hardly any increase in atomic size with increasing atomic numbers in a series of transition metals. Give reason. [AI2012]
Answer/Explanation
Answer:
Explaination:
It is because effective nuclear charge does not increase appreciably as pairing of electrons in d-orbitals take place which causes repulsion after Mn(25).
49. On what ground can you say that scandium (Z = 21) is a transition element but zinc (Z = 30) is not? [NCERT Example]
Answer/Explanation
Answer:
Explaination:
It is because Sc (21) has incompletely filled rf-orbital, that is why it is transition element, whereas Zn(30) does not have incompletely filled rf-orbitals, therefore, it is not regarded as transition element.
50. What is the lattice structure of Tc?
Answer/Explanation
Answer:
Explaination: hep.
51. Density of rf-block elements is quite high. Why?
Answer/Explanation
Answer:
Explaination:
This is due to the fact that their small atomic volume high nuclear charge and mass.
52. Ni(II) compounds are thermodynamically more stable than Pt(II) compounds. Why?
Answer/Explanation
Answer:
Explaination:
This is because that sum of ionisation energies (E1 + E2) is less in case of Ni than Pt.
53. Why do transition metals show variable oxidation states? [Delhi 2016,14(C)]
Answer/Explanation
Answer:
Explaination:
It is because electrons from both ‘s’ and d-orbitals can take part in bond formation.
54. Why the value of standard electrode potentials (E°) for Ni is more negative?
Answer/Explanation
Answer:
Explaination:
This is due to its highest value of hydration enthalpy (∆hydH°).
55. Which type of magnetic behaviour is generally shown by transition elements?
Answer/Explanation
Answer:
Explaination: Paramagnetism.
56. What is the colour of Mn2+ ions in aqueous solution?
Answer/Explanation
Answer:
Explaination: Pink.
57. Name two complex compounds formed by transition metals.
Answer/Explanation
Answer:
Explaination:
[FeCCN6)]4- and [Cu(NH3)4]2+
58. Name a catalyst used in contact process.
Answer/Explanation
Answer:
Explaination: Vanadium (V) oxide (V2O5).
59. Write any two interstitial compounds.
Answer/Explanation
Answer:
Explaination: Fe3H, TiC.
60. Give two physical properties of alloy formed by transition metals.
Answer/Explanation
Answer:
Explaination:
(i) They are usually hard.
(ii) They have often high melting points.
61. What is the geometry of chromate ion?
Answer/Explanation
Answer:
Explaination: Tetrahedral.
62. How will you convert Fe3+ ion (yellow) from Fe2+ ion (green)? Write chemical reaction equation.
Answer/Explanation
Answer:
Explaination:
63. Among lanthanoids, Ln(III) compounds are predominant. However, occasionally in solutions or in solid compounds, +2 and +4 ions are also obtained. Give reason. [AI 2012]
Answer/Explanation
Answer:
Explaination:
Lanthanoids show +3 oxidation state mostly as 2 electrons from outer 6s orbital and one electron from 5 d orbital take part in bond formation. Some show +2 and +4 oxidation states due to stability of half-filled and completely filled 4f orbitals.
64. Lanthanoids form primarily +3 ions, while the actinoids usually have higher oxidation states in their compounds, +4 or even +6 being typical. Give reason. [Delhi 2012]
Answer/Explanation
Answer:
Explaination:
In Actinoids, 5f, 6d and 7s orbitals have comparable energies and electrons from these orbitals can take part to show higher oxidation states.
65. Name an element oflanthanoid series which is well known to shown +4 oxidation state. Is it a strong oxidising agent or reducing agent? [Chennai 2019]
Answer/Explanation
Answer:
Explaination: Ce4+, it is good oxidising agent.
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