Sure Shot Questions

Chapter – 04
d-and f-Block Elements
MCQ (c) +4 (d) +5
7. Which of the following reactions are
1. Electronic configuration of a transition element X disproportionation reactions?
in +3 oxidation state is [Ar]3d5. What is its atomic (I) Cu    Cu 2  Cu
number? (II) 3MnO42  4H   2MnO4  MnO2  2H 2O
(a) 25 (b) 26
(c) 27 (d) 24 (III) 2KMnO4  K2 MnO4  MnO2  O2
2. Metallic radii of some transition elements are (IV) 2MnO4  3Mn2  2H 2O  5MnO2  4H 
given below. Which of these elements will have
highest density? (a) (I), (II) (b) (I), (II), (III)
Element Fe Co Ni Cu (c) (II), (III), (IV) (d) (I), (IV)
Metallic 126 125 125 128 8. When KMnO4 solution is added to oxalic acid
radii/pm solution, the decolourisation is slow in the
(a) Fe (b) Ni beginning but becomes instantaneous after some
(c) Co (d) Cu time because
3. Generally transition elements form coloured salts (a) CO2 is formed as the product
due to the presence of unpaired electrons. Which (b) Reaction is exothermic
of the following compounds will be coloured in
(c) MnO4 catalyses the reaction
solid state?
(d) Mn2+ acts as autocatalyst.
(a) Ag2 SO4 (b) CuF2 9. There are 14 elements in actinoid series. Which of
(c) ZnF2 (d) Cu2Cl2 the following elements does not belong to this
series?
4. On addition of small amount of KMnO4 to
(a) U (b) Np
concentrated H2SO4, a green oily compound is
(c) Tm (d) Fm
obtained which is highly explosive in nature.
10. KMnO4 acts as an oxidizing agent in acidic medium.
Identify the compound from the following.
The number of moles of KMnO4 that will be
(a) Mn2O7 (b) MnO2 needed to react with one mole of sulphide ions in
(c) MnSO4 (d) Mn2O3 acidic solution is
2 3
5. The magnetic nature of elements depends on the (a) (b)
5 5
presence of unpaired electrons. Identify the
4 1
configuration of transition element, which shows (c) (d)
5 5
highest magnetic moment.
11. Which of the following is amphoteric oxide?
(a) 3d 7 (b) 3d 5
(c) 3d 8 (d) 3d 2
Mn2O7 , CrO3 , Cr2O3 , CrO,V2O5 ,V2O4
6. Which of the following oxidation state is common (a) V2O5 , Cr2O3
for all lanthanoids?
(a) +2 (b) +3 (b) Mn2O7 , CrO3
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 (c) CrO,V2O5 18. Which of the following is a strong oxidizing agent?
[2021 C]
(d) V2O5 ,V2O4 (At. No. Mn = 25, Zn = 30, Cr= 24, Sc = 21)
12. Gadolinium belongs to 4f series. Its atomic number (a) Mn3+ (b) Zn2+
is 64. Which of the following is the correct (c) Cr3+ (d) Sc3+
electronic configuration of gadolinium? 19. The incorrect statement about interstitial
compounds
(a) [Xe]4f 7 5d 1 6s 2
(a) They are chemically reactive.
(b) [Xe]4f 6 5d 2 6s 2 (b) They are very hard.
(c) They retain metallic conductivity.
(c) [Xe]4f 8 6d 2
(d) They have high melting point. [2020]
(d) [Xe]4f 9 5s1 20. Out of the following transition elements, the
13. The magnetic moment is associated with its spin maximum number of oxidation states are shown
angular momentum and orbital angular by [2020]
momentum. Spin only magnetic moment value of (a) Sc(Z = 21) (b) Cr (Z = 24)
Cr3+ ion is (c) Mn (Z = 25) (d) Fe (Z = 26)
(a) 2.87 B.M. (b) 3.87 B.M. 21. Lanthanoid contraction is due to increase in
(c) 3.47 B.M. (d) 3.57 B.M. (a) atomic number
14. KMnO4 acts as an oxidizing agent in alkaline (b) shielding by 4f electrons
medium. When alkaline KMnO4 is treated with KI, (c) effective nuclear charge
iodide ion is oxidised to (d) atomic radius.
22. The most common and stable oxidation state of a
(a) I2 (b) IO 
Lanthanoid is
(c) IO3 (d) IO4 (a) +2 (b) +3
15. Which of the following statements is not correct? (c) +4 (d) +6.
(a) Copper liberates hydrogen from acids. 23. All the lanthanoids show +3 as the common
(b) In higher oxidation states, manganese forms oxidation state, yet Ce shows +4 state because
stable compounds with oxygen and fluorine. [2020C]
(c) Mn3+ and Co3+ are oxidizing agents in aqueous (a) It has a tendency to attain noble gas
solution. configuration.
(d) Ti2+ and Cr2+ are reducing agents in aqueous (b) It has a variable ionization enthalpy.
solution. (c) It has a tendency to gain 1 more electron.
16. Highest oxidation state of manganese in fluorides (d) It has un unpaired electron in 6s.
is +4 (MnF4) but highest oxidation state in oxides is
Assertion-Reasoning
+7 (Mn2O7) because
(a) Fluorine is more electronegative than oxygen 24. Assertion (A): Transition metals have high melting
(b) Fluorine does not posses d-orbitals point.
(c) Fluorine stabilizes lower oxidation state Reason (R): Transition metals have completely
(d) In covalent compounds, fluorine can form filled d – orbitals.
single bond only while oxygen forms double (a) Both Assertion (A) and Reason (R) are correct
bond. statements, and Reason (R) is the correct
17. Which property of transition metals enables them explanation of the Assertion (A).
to behave as catalysts? (b) Both Assertion (A) and Reason (R) are correct
(a) High melting point statements, but Reason (R) is not the correct
(b) High ionisation enthalpy explanation of the Assertion (A).
(c) Alloy formation (c) Assertion (A) is correct, but Reason (R) is incorrect
(d) Variable oxidation states statement.

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 (d) Assertion (A) is incorrect, but Reason (R) is correct 29. Assertion (A): Transition metals are good catalysts.
statement. Reason (R): V2O5 or Pt is used in the preparation of
H2SO4 by contact process.
a) Both A and R are true and R is the correct
25. Assertion (A) : Transition metals have low melting
explanation of A.
points. b) Both A and R are true but R is not the correct
Reason (R): The involvement of greater number of explanation of A.
(n - l)d and ns electrons in the interatomic metallic c) A is true but R is false.
bonding. d) A is false but R is true.
(a) Both Assertion (A) and Reason (R) are correct
30. Assertion (A): Tungsten has very high melting point.
statements, and Reason (R) is the correct Reason (R): Tungsten is a covalent compound.
explanation of the Assertion (A). a) Both A and R are true and R is the correct
(b) Both Assertion (A) and Reason (R) are correct explanation of A.
statements, but Reason (R) is not the correct b) Both A and R are true but R is not the correct
explanation of the Assertion (A). explanation of A.
c) A is true but R is false.
(c) Assertion (A) is correct, but Reason (R) is incorrect
d) A is false but R is true.
statement.
(d) Assertion (A) is incorrect, but Reason (R) is
correct statement.
26. Assertion (A): Transition metals have low melting
Case Study
points.
Reason (R): The involvement of greater number of 31. Read the given passage and answer the questions
(n – 1)d and ns electrons in the interatomic metallic that follow:
bonding.
a) Both A and R are true and R is the correct The d-block of the periodic table contains the elements
explanation of A. of groups 3-12 and are known as transition elements.
b) Both A and R are true but R is not the correct In general, the electronic configuration of these
110 12
elements is (n - 1) (n  1)d
explanation of A.
ns . The d-orbitals of
c) A is true but R is false.
d) A is false but R is true. the penultimate energy level in their atoms receive
electrons giving rise to three rows of the transition
27. Assertion: Tungsten has a very high melting point. metals i.e., 3d, 4d and 5d series. However, Zn, Cd and
Reason: Tungsten is a covalent compound. Hg are not regarded as transition elements. Transition
a) If both Assertion & Reason are true and the elements exhibit certain characteristic properties like
reason is the correct explanation of the assertion. variable oxidation states, complex formation,
b) If both Assertion & Reason are true but the formation of coloured ions and alloys, catalytic activity,
reason is not the correct explanation of the etc. Transition metals are hard (except Zn, Cd and Hg)
assertion. and have a high melting point.
c) If Assertion is true statement but Reason is false.
d) If both Assertion and Reason are false a. Why are Zn, Cd and Hg non-transition elements?
statements.
b. Which transition metal of 3d series does not show
28. Assertion (A): There is a continuous decrease in size variable oxidation states?
among lanthanoids. c. Why do transition metals and their compounds
Reason (R): Lanthanoids show lanthanoid show catalytic activity?
contraction. d. Why are melting points of transition metals high?
a) Both A and R are true and R is the correct e. Why is Cu2+ ion coloured while Zn2+ ion is
explanation of A. colourless in aqueous solution? [2020]
b) Both A and R are true but R is not the correct
f. Out of zinc and tin, whose coating is better to
explanation of A.
c) A is true but R is false. protect iron objects? [One word, 2020]
d) A is false but R is true. g. Account for the following:

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 Copper(I) compounds are white whereas
copper(II) compounds are coloured.
h. Write the formula of an oxoanion of chromium
(Cr) in which it shows the oxidation state equal to
its group number.
i. Write the formula of an oxoanion of manganese
(Mn) In which It shows the oxidation state equal
to Its group number. [Delhi 2017]
j. How would you account for the following:
Transition metals form coloured compounds? (a) Which of the following lanthanoids show +2
oxidation state besides the characteristic
k. Zn2+ salts are white while Cu2+ salts are coloured.
oxidation state +3 of lanthanoids?
Why? a) Eu b) Zn
c) Ce d) Ho
l. Why do transition elements show variable (b) Why there is a fairly regular decrease in the sizes
oxidation states? of lanthanoid with increasing atomic number?
32. Read the text carefully and answer the questions: i. Due to shielding of one 4f electron by another
The f-block consists of the two series, lanthanoids ii. Due to increasing nuclear charge along with the
(the fourteen elements following lanthanum) and series
actinoids (the fourteen elements following iii. Both (a) and (b)
actinium). Because lanthanum closely resembles iv. None of these
the lanthanoids. The chemistry of the actinoids is a) (a) b) (d)
much more complicated. The complication arises c) (c) d) (b)
partly owing to the occurrence of a wide range of (c) Which of the following have almost identical radii?
oxidation states in these elements and partly a) La and Ce b) Ho and Tb
because their radioactivity creates special c) Sm and Dy d) Hf and Zr
problems in their study. The overall decrease in (d) The Eo value for Ce 4+/Ce 3+ is:
atomic and ionic radii from lanthanum to lutetium a) +6.22V b) +1.74V
(the lanthanoid contraction) is a unique feature in c) +3.45V d) +6.78V
the chemistry of the lanthanoids. In the (e) Which of the following exhibit +4 state in oxides,
lanthanoids, La (II) and Ln (III) compounds are MO2?
predominant species. a) Nd b) All of these
c) Tb d) Pr

Question
33. Complete the following equation:
3MnO42  4H  

[2020, 2019C 1/3, Foreign 2015]
34. Complete the following equation:
2MnO4  6H   5NO2 

MnO4  8H   5e 

35. Orange colour of Cr2O72 ion changes to yellow when treated with an alkali. Why?
36. Complete the following chemical equation:

SO2  MnO4  H 2O 


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37. Account for the following:
Zr and Hf have almost similar atomic radii.
38. Name a member of the lanthanoid series which is well known to exhibit +2 oxidation state.
39. (a) Give reasons:
(i) Transition metals and their compounds show catalytic activities.
(ii) Separation of a mixture of Lanthanoid elements is difficult.
(iii) Zn, Cd and Hg are soft and have low melting points.

(b) Write the preparation of the following:

(i) Na2Cr2O7 from Na2CrO4

(ii) K2 MnO4 from MnO2

40. How would you account for the following: Transition metals form coloured compounds?

41. Assign a reason for each of the following observations:

(i) The transition metals (with the exception of Zn, Cd and Hg) are hard and have high melting and boiling
points. s
(ii) The ionisation enthalpies (first and second) in the first series of the transition elements are found to vary
irregularly.

42. Give reasons :

(i) Mn shows the highest oxidation state of +7 with oxygen but with fluorine it shows the highest oxidation
state of +4.
(ii) Transition metals show variable oxidation states.

43. Assign reason for the following: Copper (I) ion is not known in aqueous solution.

44. Give reasons for the following:

(i) Transition metals form alloys.
(ii) 𝑀𝑛2 𝑂3is basic whereas 𝑀𝑛2 𝑂7 is acidic.

45. 27. How would you account for the following?

(i) Transition metals exhibit variable oxidation states.
(ii) Transition metals and their compounds act as catalyst.

46. How would you account for the following?

(i) With the same d-orbital configuration (𝑑4 ) 𝐶𝑟 2+ is a reducing agent while 𝑀𝑛3+is an oxidising agent.
(ii) Most of the transition metal ions exhibit characteristic colours in aqueous solutions.

47. Assign reasons for each of the following :

(i) Transition metals generally form coloured compounds.
(ii) Manganese exhibits the highest oxidation state of +7 among the 3rd series of transition elements.

48. What are alloys? Name an important alloy which contains some of the lantanoid metals. Mention its uses.

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49. Why do transition elements exhibit higher enthalpies of atomization?

50. Account for the following:

i) Transition metals show variable oxidation states.
ii) Zn , Cd and Hg are soft metals.

51. The elements of 3d transition series are given as:

𝑆𝑐 𝑇𝑖 𝑉 𝐶𝑟 𝑀𝑛 𝐹𝑒 𝐶𝑜 𝑁𝑖 𝐶𝑢 𝑍𝑛
Answer the following:
𝑜
(a) Copper has exceptionally positive 𝐸𝑀 2+ /𝑀 value. Why?

(b) Which element is a strong reducing agent in +2 oxidation state and why?
(c) 𝑍𝑛2+ salts are colourless. Why?

52. Assign reasons for the following:

(i) The second and third rows of transition elements resemble each other much more than they resemble the
first row.
(ii) 𝐾2 [𝑃𝑡𝐶𝐼6 ] is a well – known compound whereas the corresponding Ni compound is not known.
(iii) In transition series, with an increase in atomic number, the atomic radius does not change very much.

53. (a) Complete the following chemical reaction equations:

(i) 𝑀𝑛𝑂4− (𝑎𝑞) + 𝐶2 𝑂42− (𝑎𝑞) + 𝐻 + (𝑎𝑞) →
(ii) 𝐶𝑟2 𝑂72− (𝑎𝑞) + 𝐹𝑒 2+ (𝑎𝑞) + 𝐻 + (𝑎𝑞) →
(b) (i) 𝑀𝑛2+ is much more resistant than 𝐹𝑒 2+ towards oxidation.
(ii) Many of the transition elements are known to form interstitial compounds.
(iii) Among lanthanoids, Ln (III) compounds are predominant. However, occasionally in solutions or in solid
compounds, +2 and +4 ions are also obtained.

54. Give reasons for the following:

(a) Transition metals have high enthalpies of atomization.
(b) Among the lanthanoids, Ce(III) is esily oxidized to Ce(IV).
(c) 𝐹𝑒 3+ |𝐹𝑒 2+ redox couple has less positive electrode potential then 𝑀𝑛3+ |𝑀𝑛2+ couple.
(d) Copper (I) has 𝑑10 configuration, while copper (II) has 𝑑9 configuration, still copper (II) is more stable in
aqueous solution than copper (I).
(e) The second and thirdtransition series elements have almost similar atomic radii.
55. (a) Assign reasons for the following:
(i) In the series Sc(𝑍 = 21) 𝑡𝑜 𝑍𝑛(𝑍 = 30), the enthalpy of atomisation of Zn is the lowest.
(ii) Zr and Hf have almost identical radii.
(iii) Transition metals show variable oxidation states.
𝑜
(iv) The 𝐸𝑀 2+ /𝑀 value for copper is positive (+0.34 𝑉).

(b) Although +3 oxidation state is the characteristic oxidation state of lanthanoids but cerium shows +4
oxidation state also. Why?

56. Calculate the spin-only moment of 𝐶𝑜 2+ (𝑍 = 27) by writing the electronic configuration of Co and 𝐶𝑜 2+.

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57. Give reason and select one atom/ion which will exhibit asked property:
(i) 𝑆𝑐 3+ or 𝐶𝑟 3+ (exhibit diamagnetic behaviour)
(ii) 𝐶𝑟 𝑜𝑟 𝐶𝑢 (high melting and boiling point)

58. (i) Which ion amongst the following is colourless and why?
𝑇𝑖 4+ , 𝐶𝑟 3+ , 𝑉 3+,
(Atomic number of 𝑇𝑖 = 22, 𝐶𝑟 = 24, 𝑉 = 23)
(ii) Why is 𝑀𝑛2+ much more resistant than 𝐹𝑒 2+ towards oxidation?
(iii) Highest oxidation state of a metal is shown in its oxide or fluoride only. Justify the statement.

59. (i) Silver atom has completely filled d-orbitals in its ground state, it is still considered to be a transition element.
Justify the statement.
0
(ii) Why are 𝐸𝑀 2+ /𝑀 values of 𝑀𝑛 𝑎𝑛𝑑 𝑍𝑛 more negative than expected?

(iii) Why do transition metals form alloys?

60. Give reasons for the following statements:

(a) Copper does not displace hydrogen from acids.
(b) Transition metals and most of their compounds show paramagnetic behaviour.
(c) Zn, Cd and Hg are soft metals.

61. (i) Why are melting points of transition metals high?

(ii) Why the transition metals generally form coloured compounds?
(iii) Why 𝐸° value for 𝑀𝑛3+ /𝑀𝑛2+ couple is highly positive?

62. Define transition metals. Why Zn, Cd and Hg are not called transition metals? How is the variability in oxidation
states of transition metals different from that of p-block elements?

63. (a) Write any two consequences of lanthanoid contraction.

(b) Name the element of 3𝑑 series which exhibits the largest number of oxidation states. Give reason.

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