MP BOARD CLASS-10th-12th Model Question Paper-2025-26

 

Subject:- Chemistry

Class:- 12th

D and F Block Elements

Objective Question 

1.General electronic configuration of transition element is
(a) (n – 1)d^{1 – 10} ns¹
(b) (n – 1)d¹⁰ns²
(c) (n – 1)d¹d^{1 – 10}ns²
(d) (n – 1)d⁵ns¹.

2. Silver nitrate produces a black stain on the skin due to

(a) being a strong reducing agent

(b) its corrosive action

(c) formation of complex compound

(d) its reduction to metallic silver
3.Reason of Lanthanide contraction is :
(a) Negligible screening effect of f – orbitals
(b) Increasing nuclear charge
(c) Decreasing nuclear charge
(d) Decreasing screening effect.
4. In Fe(CO)₅, the Fe-C bond possesses:

(a) ionic character

(b) sigma character only

(c) pi character

(d) both sigma and pi characters
5. Chromyl chloride test confirms the presence of :
(a) Cl^–       (b) SO₄^2-      (c) Cr³⁺    (d) Cr³and Cl^–

Note:- Chromyl chloride test is a qualitative analysis test used for the conformation for Cl− ion.

A sample of chlorine-containing salt is heated with conc H2​SO4​ in presence of K2​Cr2​O7​, deep red vapours of chromyl chloride are evolved.

NaCl+H₂​SO_4​→NaHSO₄​+HCl

K_2​Cr₂​O₇​+2H₂​SO₄​→2KHSO_4​+2CrO_3​+H₂​O

CrO₃​+2HCl→CrO_2​Cl₂​+H2​O

          Chromyl chloride

         (deep red vapour)

6.Formula of Mohr’s salt is :
(a) FeSO₄.7H₂O
(b) FeSO₄.(NH₄)2SO₄.6H₂O
(c) CU(OH)₂.CUCO₃.6H₂O
(d) Fe₂O₃.3H₂O.

7. German silver an alloy of – Cu+Zn+Ni
8. The outer electronic configuration of chromium is :
(a) 4s¹, 3d⁵   (b) 4s², 3d⁴   (c) 4s⁰, 3d⁶   (d) 4s²,3d⁵.
9. The equivalent weight of KMnO₄ is alkaline medium will be
(a) 31.60   (b) 52.66   (c) 79.00     (d) 158.00

10. The Lanthanide which is widely used
(a) Lanthanum   (b) Nobelium   (c) Thorium     (d) Cesium.
11. Electronic configuration of Gadolinium is :
(a) [X_e]4f⁶,5d⁹,6s²                (b) [X_e]4f⁷,5d¹6s²
(c) [X_e]4f³,5d⁵,6s²               (d) [X_e]4f⁶,5d²,6s².

12. Transition element

(a) Forms to coloured compound  (b) Exhibits variable valency

(c) Forms the Alloy               (d) All of the above.

13. Element of atomic number 29 will be the element of the following block of periodic table

(a) s-block   (c) d-block   (b) p-block   (d) f-block.

14. With increasing nuclear charge in the 3d transition series shielding effect will

(a) Increase                   (b) Decrease

(c) Remain constant            (d) First decrease then increase.

15. Which transition element has highest oxidation state

(a) Sc   (b) Ti     (c) Mn    (d) Zn

16. Variable valency is shown by

(a)Non-metal (b) Metal (c) Normal element (d) Transition elements

17. Transition elements are generally paramagnetic because they

(a) Having high melting point and boiling point

(b) Having incomplete orbital

(c) Having unpaired electron

(d) Become malleable and tensile.

18. Transuranic elements are those elements which are

(a) Heavier than uranium          (b) Lighter than uranium

(c) Similar weight as electrons     (d) Isotopes of uranium.

19. The no. of unpaired electrons in chromium atom is

(a) 3      (b) 4    (c) 5     (d) 6

20. Which of the following form interstitial compound:

(a) Fe       (b) Co  (c) Mn            (d) All of these.
21.Fe, Co, Ni are magnetic substance of which type
(a) Paramagnetic                   (b) Ferromagnetic 

 (c) Diamagnetic                    (d) Antiferromagnetic.:
22. Number of unpaired electrons in Fe⁺² ion is :
(a) 0     (b) 4     (c) 6       (d) 3.
23. In which of the compounds Mn shows highest oxidation state
(a) K₂MnO₄    (b) KMnO₄     (c) MnO₂    (d) Mn₃O₄.
24. The atomic radius and ionic radius of Zr and Hf are similar due to
(a) Diagonal relationship     (b) Both are present in same group
(c) Lanthanide contraction  (d) Similar chemical properties.
25. Transition elements are coloured due to
(a) Paired electron in d – orbital    (b) Paired electron in f – orbital
(c) Unpaired electron in d – orbital    (d) None of these
26.Stability of ferric ion is due to
(a) Half filled d – orbital           (b) Half filled f – orbital
(c) Completely filled d – orbital     (d) Completely filled f – orbital.
27. Metals Fe, Co, Ni are known as Ferrous metals

28.Ionic size of trivalent cations are Decreases with increase in atomic numbers.

29.The transition metals having lower oxidation state shows Basic nature

30.K₂Cr₂O₇ is a strong Oxidizing agent, which gives nascent oxygen.

31. Zn shows only +2 oxidation state.

32. f – block elements are known as Inner transition elements.

33. Transition elements and their compounds act as Catalyst

34. General electronic configuration of inner transition element is (n-2) f^1–14(n–1) d^1–2(n –1) d^1–2 ns²

35. Chemical form of Potassium manganate is K₂MnO₄

36. d – block elements are also known as Transitional Elements.

37. Mercury is liquid and its oxidation state is +1 and +2.

38. In all transition elements normal oxidation state is +2.

39. Zn, Cd, Hg not show variable oxidation state.

40. Plutonium used as fuel in nuclear reaction and in formation of atomic bomb.

41. Transition elements easily form interstitial compounds

42. Which is colourless Cu²⁺or Cu⁺? Answer- Cu⁺²

43. In a reaction KMnO₄ is replaced by K₂MnO₄ then what will be change in oxidation state of Mn? Answer- 1 (+7 to +6 )

44. Which series shows higher oxidation state lanthanides or actinides? Answer- Actinides

45. Which oxidation state of lanthanum is most stable?Answer- +3

46. Write the equivalent weight of K₂Cr₂O7 in acidic medium. Answer- 49

47.  How many unpaired electrons are present in Fe³⁺? Answer- 5

48. Give the name of oxidising agent used in chromyl chloride test Answer- K₂Cr₂O₇

49. Out of d – block elements, Zn does not show variable valencies, why? Answer- Completely filled ‘d’ orbitals

50. What is Lunar caustic? Answer - AgNO₃ (Silver nitrate)

51. In d – block elements Zn does not exhibit variable oxidation state. Why? Answer- Due to fully filled d – orbitals

52. What is the alkaline solution of HgCl₂ and KI known as?

Answer- Nessler’s reagent

53. Coin Metal- Cu, Ag, Au

54. Rare Earth elements- F- Block Elements

55.Metal used for hydrogenation of oil – Ni

56.Which of the following metals does not liberate hydrogen gas on reacting with acid?

(A) Fe     (B) Zn     (C) Cu      (D) Mg 

57.Aqueous solution of which of the following ions is coloured?

 (A) Cu⁺¹   (B) Ag⁺¹     (C) Fe⁺¹       (D) Zn²⁺

 

58.Which of the following gives yellow or brown precipitate with Nessler's reagent?

(A) CO₂    (B) NH₃    (C) NaCl             (D) KI 

59. Green Vitriol – FeSO₄.7H₂O

60. Blue Vitriol – CuSO₄.5H₂O

61. White Vitriol – ZnSO₄.7H₂O

62. Mohar Salt- FeSO₄(NH₄)₂ SO₄.6H₂O

Very Short Answer Type Questions

1.Actinide contraction is greater from element to element than lanthanide contraction. Why?

Answer:- This is due to poor shielding effect by 5f electrons in the actinoids than that of 4f electrons in the lanthanoids.

2.Explain Cu⁺ is colourless while Cu⁺² is coloured.

Answer:- If a transition metal contain unpaired electron, it shows paramagnetism and forms coloured compound. In Cu⁺d – orbital is partially filled (3d⁹) thus Cu⁺ is colourless and diamagnetic while Cu⁺² is coloured and paramagnetic.

3. Why are Mn²⁺ compounds more stable than Fe²⁺ towards oxidation to their +3 oxidation state?

Answer:- Mn⁺² has stable electronic configuration [Ar]4r⁰3d⁵ and they do not easily change to Mn⁺³, Fe⁺² [Ar] 4s⁰3d⁶ on oxidation forms Fe⁺³ [Ar] 4s⁰3d⁵ a more stable configuration.

4. What are interstitial compounds? Why are such compounds well known for transition metals?

Answer:- Most of the transition elements form interstitial compounds at high temperature with atoms of non – metallic elements like H,B,C,N, Si etc. Small atoms of these non – metallic elements fit in the interstitial voids of crystal lattice of transition elements. These are called interstitial compounds.

5. What are alloys? Name an important alloy which contains some of the lanthanoid metals. Mention its uses.
Answer:- An alloy is a homogeneous mixture of two or more metals or metals and non – metals. An important alloy contains lanthanoid metal is mischmetal which contains 50% Cerium and 25 % Lanthanum, with small amounts of Nd (Neodymium) and Pr (Praseodymium). It is used in Mg – based alloy to produce bullets, shell and lighter flints.

6. Ti²⁺, V²⁺ and Cr²⁺ are strong reducing agents. Why?

Answer:-For Ti²⁺, V²⁺ and Cr²⁺, values of M²⁺/M is negative which justify that they are strongly reducing.

7. Write the unit of magnetic moment.

Answer:- Bohr Magneton (BM).

8.What is lanthanoid contraction? What are the consequents of lanthanoid contraction?

Answer:-Interesting feature of the atomic size of lanthanides is that on moving down the group steady decrease in atomic size is observed. The shape of f – orbital is in such a way that its shielding effect is minimum, there fore on addition of extra electron in f – subshell only attractive force increases. The steady decrease (contraction) in size of fourteen lanthanide elements (La³⁺1.06 Å to Lu³⁺ 0.8 Å) by a value of about 0.2Å is known as lanthanide contraction.

Reason:
1. The new electrons in lanthanides instead of going to outermost shell enters (n – 2)f – suborbital as a result of which force of attraction increases between electron and nucleus due to which atom or ion contracts.

2. Electron entering in (n – 2) f – suborbital have negligible or zero shielding effect over electrons present in the last orbit. In addition the shape of f – suborbital is not favorable for the shielding effect of electrons. Thus, lanthanide contraction occurs.

9.What are Transition elements? They show metallic character. Why?
Answer:- Elements whose atoms in their ground state or ions in their common oxidation states have incomplete or partially filled d – orbitals are called transitional elements. They are in group 2 to 13. Example : Fe, Ni, Co, etc.
General formula : (n – 1)d^{1 – 10}ns^{1 – 2}

Metallic character of an element depends on its tendency to form cation by loosing one or more electrons from its atom. All transitional elements are metals because they contain one or two electrons in their outermost shell which can be easily lost due to low ionisation energy. Thus, they are metallic in nature.

10.Why do transition metals exhibit variable oxidation states?
Answer:- Transition metals exhibit variable valency because the energy subshell (n – 1 )d and ns are very close. Thus, possibility to lose electrons from ns subshell as well as from (n -1 )d subshell is very much if there are unpaired electrons. So oxidation states of these metals may increase. In these elements Mn shows maximum variable valencies.

11. Transition elements form alloy easily. Explain.
Answer:-It is the homogeneous mixture of two or more metals or metals with non – metals. Alloys are made to confer the property of metals. Transition elements have great tendency to form alloys because these elements have similar atomic size and can mutually substitute their positions in their crystal lattice. Alloys are comparatively hard and have higher m.p. than the elements from which they are made.

12. The radius of Fe²⁺ ion is smaller than the radius of Mn²⁺ion, why?
Answer:-The atomic number of Fe (26) is more than the atomic number of Mn (25). Due to higher value of atomic number, iron nucleus contains more protons. Hence the force of attraction between the nucleus and the electrons of outermost orbit is more. Due to strong attractive force of the nucleus the electron cloud is pulled inwards which results in smaller size of Fe²⁺ ion as compared to Mn²⁺ ion.

13. Transition metals possess the ability to form complex compounds. Explain.

Answer- Cause of formation of complex compounds by Transition metals

• Small size of ions of these elements and high nuclear charge due to which these ions attract ligands.
• They possess vacant d – orbitals in order to accomodate the electron pair donated by ligand.

14. Zn, Cd and Hg do not show the properties of Transition elements.

Answer- Elements in which (n – 1) d – orbital is partially filled are known as Transition elements Whereas in Zn [3d¹⁰4s²], in Cd [4d¹⁰ 5s²] and in Hg [5d¹⁰6s²] state is found. Therefore, these do not show the properties of Transition elements.

15. Why is Ti known as a wonder metal?

Answer- Titanium is a shining white metal. It is extended strong (harder than steel), has high m.p. Good conductor of electric current resistant to corrosion and light metal. Due to all these qualities, it is called wonder metal.

16.Write five differences between Lanthanide and Actinide.
Answer:-Differences between Lanthanides and Actinides Elements
Lanthanides Elements:

• Lanthanides show oxidation state of + 3 mainly and +2 and +4 in few compounds.
• Tendency to form complex compound is low.
• Lanthanide compounds are less basic than actinide compounds.
• These do not form oxo – ions.
• Except promethium all are non – radioactive elements.
• Last electron enters in 4f – subshell.

Actinides Elements:

• Actinides show + 3 oxidation state together with + 4, + 5 and +6 in all compounds.
• Tendency to form complex compund is more than lanthanides.
• Actinide compounds are more basic.
• Actinides form oxo – ions as UO₂⁺, NpO⁺, PuO₂⁺, etc.
• All actinides are radioactive.
• Last electron enters in 5f – subshell.

17. Write any five main differences between d – and f – Block elements.
Answer:-Differences between d and f – Block Elements :
d – Block Elements:

• Two shells n and (n – 1) are incomplete.
• Last electron enters the d – orbital of penultimate shell.
• d – block elements are normally called Transitional element.
• d – block elements are available in nature.
• These elements exhibit variable oxidation state.
• These elements are stable.

f – Block Elements:

• Three shells n, (n – 1) and (n – 2) are incomplete.
• Last electron enters the orbital of antipenultimate (n – 2) shell.
• f – block elements are normally called Inner Transitional element.
• f – block elements are very rare. Therefore, they are known as Rare Earth elements.
• These elements also exhibit variable oxidation state.
• These elements are less stable and many are radioactive.

18.Transition metals and many of their compounds show paramagnetic behavior

Answer:-Paramagnetic substance is one which is attracted by magnetic field. It arises due to presence of unpaired electron in atom, ion or molecule. Most of the transition elements and compounds are paramagnetic in nature. This is due to fact that transition elements involve partially filled d – subshell and their atom and ion contain unpaired electron.

19. The enthalpies of atomisation of the transition metals are high.

Answer:-Transition elements have high effective nuclear charge and a large number of valence electrons. Therefore, they form very strong metallic bonds. As a result, the enthalpy of atomization of transition metals is high.

20. The transition metals generally form coloured compounds.

The colour of transitional metal ions is due to partially filled (n –1)d orbitals. In transitional metal ions which contain unpaired d electrons, transition of electrons takes place from one d – orbital to another d – orbital. During this transition it absorbs some radiation of visible light and reflects the remaining radiation in the form of coloured light. Thus, the colour of the ion is complementary to the colour absorbed by it.
For example:

[Cu(H₂O)₆]²⁺ ion appears blue because it absorbs the red colour of the visible light for electron promotion and reflects its complementary blue colour.

21. Transition metals and their many compounds act as good catalyst.

4. Transition elements act as good catalysts in chemical reaction in the hydrogenation of Ni metal, in contact process of manufacture of SO₃, Pt and in manufacture of NH₃ by Haber process Fe acts as catalyst. In the method of preparation of O₂ by heating KClO₃, MnO₂ acts as catalyst.

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