Class 12 d and f block elements MCQs

Chemistry class 12 d and f block elements MCQs, Assertion-Reason questions, and case-based study questions are given here. You can download the Word file of the given questions, which is linked below.

Class 12 d and f Block Elements MCQs

MULTIPLE CHOICE QUESTIONS

1. The electronic configuration of a transition element X in +3 oxidation state is [Ar]3d⁵. What is its atomic number?

(a) 25 (b) 26 (c) 27 (d) 24

2. 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

3. Generally, transition elements form colored salts due to the presence of unpaired electrons. Which of the following compounds will be colored in solid state?

(a) Ag₂SO₄ (b) CuF₂ (c) ZnF₂ (d) Cu₂Cl₂

4. 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.

(a) Mn₂O₇ (b) MnO₂ (c) MnSO₄ (d) Mn₂O₃

5. The magnetic nature of elements depends on the presence of unpaired electrons. Identify the configuration of transition element, which shows highest magnetic moment.

(a) 3d⁷ (b) 3d⁵ (c) 3d⁸ (d) 3d²

6. Which of the following oxidation state is common for all lanthanides?

(a) +2 (b) +3 (c) +4 (d) +5

7. Which of the following reactions are disproportionation reactions?

(a) Cu⁺ → Cu²⁺ + Cu

(b) 3MnO₄^– + 4H⁺ → 2MnO₄^–+ MnO₂ + 2H₂O

(d) 2MnO₄^– + 3Mn²⁺ + 2H₂O → 5MnO₂ + 4H⁺(i) a, b (ii) a, b, c (iii) b, c, d (iv) a, d

8. When KMnO₄ solution is added to oxalic acid solution, the decolorization is slow in the beginning but becomes instantaneous after some time because

(a) CO₂ is formed as the product. (b) Reaction is exothermic.

9. There are 14 elements in actinoid series. Which of the following elements does not belong to this series?

(a) U (b) Np (c) Tm (d) Fm

10. KMnO₄acts as an oxidising agent in acidic medium. The number of moles of KMnO₄ that will be needed to react with one mole of sulphide ions in acidic solution is

(a) 2 / 5 (b) 3 / 5 (c) 4 / 5 (d) 1 / 5

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11. Which of the following is amphoteric oxide?
Mn₂O₇, CrO₃, Cr₂O₃, CrO₅, V₂O₅, V₂O₄

(a) V₂O₅, Cr₂O₃ (b) Mn₂O₇, CrO₃ (c) CrO₅, V₂O₅ (d) V₂O₅, V₂O₄

12. Gadolinium belongs to 4f series. Its atomic number is 64. Which of the following is the correct electronic configuration of gadolinium?

(a) [Xe] 4f⁷5d¹6s² (b) [Xe] 4f⁶5d²6s² (c) [Xe] 4f⁸6d² (d) [Xe] 4f⁹5s¹

13. Interstitial compounds are formed when small atoms are trapped inside the crystal lattice of metals. Which of the following is not the characteristic property of interstitial compounds?

(a) They have high melting points in comparison to pure metals.

(b) They are very hard.

(d) They are chemically very reactive.

14. The magnetic moment is associated with its spin angular momentum and orbital angular momentum. Spin only magnetic moment value of Cr³⁺ ion is

(a) 2.87 BM (b) 3.87 BM (c) 3.47 BM (d) 3.57 BM

15. KMnO₄ acts as an oxidising agent in alkaline medium. When alkaline KMnO₄ is treated with KI, iodide ion is oxidised to

(a) I₂ (b) IO^– (c) IO₃^– (d) IO₄^–

16. Which of the following statements is not correct?

(a) Copper liberates hydrogen from acids.

(b) In its higher oxidation states, manganese forms stable compounds with oxygen and fluorine.

(d) Ti²⁺ and Cr²⁺ are reducing agents in aqueous solution

17. When acidified K₂Cr₂O₇ solution is added to Sn²⁺ salts then Sn²⁺ changes to

(a) Sn (b) Sn³⁺ (c) Sn⁴⁺ (d) Sn⁺

18. 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.

(d) in covalent compounds fluorine can form single bond only while oxygen forms double bond.

19. Although Zirconium belongs to 4d transition series and Hafnium to 5d transition series even then they show similar physical and chemical properties because

(a) both belong to d-block.

(b) both have same number of electrons.

(d) both belong to the same group of the periodic table

20. Why is HCl not used to make the medium acidic in oxidation reactions of KMnO₄ in acidic medium?

(a) Both HCl and KMnO₄ act as oxidising agents.

(b) KMnO₄ oxidises HCl into Cl₂ which is also an oxidising agent.

(d) KMnO₄ acts as a reducing agent in the presence of HCl.

Read All important questions and MCQs of the Biomolecule chapter

Class 12 d and f Block elements MCQs

(a)Assertion and reason both are correct statement and reason is correct

explanation for assertion.

(b) Assertion and reason both are correct statement and 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.

1. Assertion: The maximum oxidation state of chromium in its compounds is + 6.
Reason : Chromium has only six electrons in ns and (n – 1) d-orbitals.

2. Assertion: Cuprous salts are diamagnetic in nature.
Reason : Cu⁺ion has filled 3d-orbitals.

3. Assertion: Ce⁴⁺ is used as oxidising agent in volumetric analysis.
Reason : Ce⁴⁺ has the tendency to acquire + 3 oxidation state.

4. Assertion: Acidified K₂Cr₂0₇ solution becomes green when SO₂ is passed through it.
Reason : SO₂ acts as an oxidising agent in the reaction.

5. Assertion: Manganese shows a number of oxidation states.
Reason : The difference of energy between 3d and 4s sub shells is large.

6. Assertion: Actinoids show greater number of oxidation states than lanthanoids.
Reason : Actinoids are radioactive.

7. Assertion: Ionisation of transition metals involves loss of ns electron before (n- 1)d

electrons.
Reason : Filling of ns-orbitals takes placed before (n-1)d orbitals.

8. Assertion: The chemistry of the actinoid elements is not so smooth as that of lanthanoids.
Reason : Lanthanoids show wide range oxidation states.

9. Assertion: Zn²⁺ ion is diamagnetic in nature.
Reason: The electrons are lost from 4s-orbital to form Zn ion.

10. Assertion: To a solution of potassium chromate if a strong acid is added, it changes its colour from yellow to orange.
Reason: The colour change is due to change in oxidation state of potassium chromate.

d and f Block Elements Case-Based questions

Read the paragraph and answer the following questions

1. The f-block elements are those in which the differentiating electrons enters the antepenultimate (n-2) f orbitals. There are two series of f-Block elements corresponding to filling of 4f and 5f-orbitals. The series of 4f-orbitals is called lanthanoids and the series of 5f-orbitals is called actinoids. Lanthanoids and actinoids show different oxidation states depending upon stability of f⁰, f⁷ and f¹⁴ configurations, though the most common oxidation states is +3.

Lanthanoids and actinoids show some common characteristics like contraction, magnetic behaviour, colored compound formation and at the same time they are also different in some perspectives like complex formation, oxidation state etc.

(a) Name the element of Lanthanoids which show +4 oxidation state?

(b) Actinoid contraction is greater from element to element than Lanthanoid contraction.

(ii) Why Actinoids have more tendency to form complex?

2. The unique behaviour of Cu, having a positive E^o value accounts its inability to liberate H₂ from acids. Only oxidizing acids like HNO₃ and conc. H₂SO₄ reacts with Cu. The stability of the half-filled d subshell in Mn²⁺ and the completely-filled d¹⁰ configuration in Zn²⁺ are related to their E^o(M³⁺/M²⁺) values.

The low values for Sc reflect the stability of Sc³⁺ which has a noble gas configuration. The high value for Mn shows that Mn²⁺ having d⁵ is stable where as low value for Fe shows extra stability of Fe³⁺ having d⁵. The low value for V is related to the stability of V²⁺ having half-filled t_2g level.

(a)Why is E^o(Cu²⁺/Cu) value exceptionally positive?

(b)Why is E^o(Mn²⁺/Mn) value highly negative as compared to other elements?

(c)Which is a stronger reducing agent Cr²⁺ or Fe²⁺? Give reason.

(c)What is lanthanoid contraction? Write down one consequence of it.

3. Within the 3d series Sc exhibits only +3 oxidation state. Mn exhibits oxidation states in aqueous solution from +2 to +7. Ranging from Mn²⁺ to MnO₄^– . Likewise iron forms both Fe²⁺ and Fe³⁺. Cr and Mn forms CrO₄^2- and MnO₄^–owing to their willingness to form multiple bonds. In the 3d series up to Mn and for the 4d, 5d metals up to Ru and Os, the maximum oxidation state corresponds to the number of outer shell electrons.

(a)Why is Cr²⁺ reducing and Mn³⁺ oxidizing when both have d⁴ configuration?

(b)The highest oxidation state of a metal exhibited in its oxide or fluoride only. Why?

(c)Why is Cr²⁺ a stronger reducing agent than Fe²⁺?

(ii) Which of the 3d series of the transition metals exhibits the largest number of oxidation states and why?

4. Potassium permanganate, KMnO₄ is prepared by fusion of pyrolusite, MnO₂ with KOH in the presence of an oxidizing agent like KNO₃. This produces the dark green potassium manganate K₂MnO₄ which disproportionate in a neutral or acidic solution to give purple permanganate ion. Potassium permanganate is an important oxidizing agent in acidic, alkaline as well as neutral medium. Potassium permanganate has no unpaired electron. So, d-d transition is not possible.

(a) What is reason for purple colour of KMnO₄?

(b) What happens when KMnO₄ is heated?

5. Most of the compounds of the transition metals are coloured in the solid or in solution states. The colour of the transition metal ions arise from the excitation of electrons from the d orbitals of lower energy to the d orbitals of higher energy. The energy required for d-d transition excitation is available in the visible range. Transition metal ions have the tendency to absorb certain radiations from the visible region and exhibit the complementary colour.

The transition metal ions which have completely-filled d-orbitals are colourless as the excitation of electrons is not possible within d orbitals. The transition metal ions which have completely empty d-orbitals are also colourless. In certain oxysalts of transition elements like KMNO₄, K₂Cr₂O₇, there are no unpaired electrons at the central atom but they are deep in colour. The colour of these compounds is due to charge transfer spectrum. For example, in MnO₄^–, an electron is transferred momentarily from O²^– to O^– and from Mn⁺⁷ to Mn⁺⁶.

(a) Why does K₂Cr₂O₇ gives coloured solution in water?

(b) Why is [Cr(H₂O)₆]³⁺ a coloured ion?

(ii) Out of Sc³⁺ and Ti³⁺, which one is colourless in aqueous solution.

On addition of small amount of KMnO₄ to concentrated H₂SO₄, a green oily compound X is obtained which is highly explosive in nature. Identify the compound X. Also write the equation.

6. Transition elements show colour which depends on d-d transition. Presence of unpaired electrons are responsible for d-d transition. Transition metal ions having paired d-electrons are colorless. In certain oxysalts of transition elements like KMnO₄, K₂Cr₂O₇, there are no unpaired electrons in d-orbital of central atom but they are coloured. The colour of these compounds is due to charge transfer spectrum. For example, in MnO₄-, an electron is transferred O- to Mn.

Based on the information, Answer the following questions-:

(a) (i) When orange solution containing Cr2O72- ion is treated with an alkali, a yellow solution is formed. Explain why?

(ii) Out of Sc3+ and Ti3+, which one is colourless in aqueous solution?

(b) On addition of small amount of KMnO4 to concentrated H₂SO₄, a green oily compound (X) is obtained which is highly explosive in nature. Identify the compound X.