Chemistry

The d-Block and f-Block Elements

Question:

The second and third rows of tfansition elements resemble each other much more than they resemble the first row. Explain why?

Answer:

Due to lanthanide contraction, the atomic radii of the second and third row transition elements are almost same. Therefore, they resemble each other much more as compared to first row elements.

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The d-Block and f-Block Elements

Q 1.

Which of the following will not act as oxidizing agents?
(a) CrO3  (b) MoO3(c) WO3   (d) CrO42-

Q 2.

Name the members of the lanthanoid series which exhibit+4oxidatk>nstatesandthosewhichexhibit +2 oxidation states. Try to correlate this type of behaviour with the electronic configurations of these elements.

Q 3.

Although fluorine is more electronegative than oxygen, but the ability of oxygen to stabilize higher oxidation states exceeds that of fluorine. Why?

Q 4.

A solution of KMnO4 on reduction yields either a colourless solution or a brown precipitate or a green solution depending on pH of the solution. What different stages of the reduction do these represent and how are they carried out?

Q 5.

Transition elements show high melting points. Why?

Q 6.

When Cu2+ ion is treated with KI, a white precipitate is formed. Explain the reaction with the help of chemical equation.

Q 7.

What may be the stable oxidation state of the transition element with the following delectron configurations in the ground state of their atoms: 3d3,3d5, 3d8 and 3d4?

Q 8.

Compare the chemistry of actinoids with that of lanthanoids with reference to:
(i) Electronic configuration
(ii) Oxidation states
(iii) Chemical reactivity

Q 9.

E of Cu is +0.34 V while that of Zn is -0.76 V. Explain.

Q 10.

Explain giving reasons:
(i)Transition metals and many of their compounds show paramagnetic behaviour.
(ii)The enthalpies of atomisation of the transition metals are high.
(iii)The transition metals generally form coloured compounds.
(iv)Transition metals and their many compounds act as good catalyst

Q 11.

Predict which of the following will be coloured in aqueous solution? Ti3+, V3+,Cu+, Sc3+, Mn2+, Fe3+ and Co2+ Give reasons for each.

Q 12.

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

Q 13.

Why E ° value for Mn, Ni and Zn are more negative than expected?

Q 14.

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

Q 15.

Assertion (A): The highest oxidation state of osmium is +8.
Reason (R): Osmium is a 5d-block element.

Q 16.

Describe the preparation of potassium dichromate from iron chromite ore. What is the effect of increasing pH on a solution of potassium dichromate?

Q 17.

What is meant by disproportionation? Give two examples of disproportionation reaction in aqueous solution.

Q 18.

What are inner transition elements? Decide which of the following atomic numbers are the atomic numbers of the inner transition elements: 29,59,74,95,102,104.

Q 19.

Which of the following reactions are disproportionation reactions?
ncert-exemplar-problems-class-12-chemistry-d-f-block-elements-4

Q 20.

Which of the following ions show higher spin only magnetic moment value?
(a) Ti3+ (b) Mn2+ (c) Fe2+ (d)  Co3+

Q 21.

When a chromite ore (A) is fused with sodium carbonate in free excess of air and the product is dissolved in water, a yellow solution of compound (B) is obtained. After treatment of this yellow solution with sulphuric acid, compound (C) can be crystallized from the solution. When compound (C) is treated with KCl, orange crystals of compound (D) crystallise out. Identify A to D and also explain the reactions.

Q 22.

Mention the type of compounds formed when small atoms like H, C and N get trapped inside the crystal lattice of transition metals. Also give physical and chemical characteristics of these compounds.

Q 23.

In what way is the electronic configuration of the transition elements different from that of the non transition elements?

Q 24.

The chemistry of the actinoid elements is not so smooth as that of the lanthanoids. Justify this statement by giving some examples from the oxidation state of these elements.

Q 25.

Which is the last element in the series of the actinoids? Write the electronic configuration of this element. Comment on the possible oxidation state of this element

Q 26.

Com pare the general characteristics of the first series of the transition metals with those of the second and third series metals in the respective vertical columns. Give special emphasis on the following points:
(i) electronic configurations
(ii) oxidation states
(iii) ionisation enthalpies and
(iv) atomic sizes

Q 27.

Metallic radii of some transition elements are given below. Which of these elements will have highest density?
ncert-exemplar-problems-class-12-chemistry-d-f-block-elements-2

Q 28.

Reactivity of transition elements decreases almost regularly from Sc to Cu. Explain.

Q 29.

(a) Transition metals can act as catalysts because these can change their oxidation state.
How does Fe(III) catalyse the reaction between iodide and persulphate ions?
(b) Mention any three processes where transition metals act as catalysts.

Q 30.

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

Q 31.

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

Q 32.

KMnO4 acts as an oxidizing agent in acidic medium. The number of moles of KMn04 that will be needed to react with one mole of sulphide ions in acidic solution is
ncert-exemplar-problems-class-12-chemistry-d-f-block-elements-8

Q 33.

Which of the following actinoids show oxidation states up to +7?
(a) Am (b) Pu (c) U (d) Np

Q 34.

Ionisation enthalpies of Ce. Pr and Nd are higher than Th, Pa and U. Why?

Q 35.

ncert-solutions-for-class-12-chemistry-the-d-and-f-block-elements-1

Q 36.

Explain briefly how+2 state becomes more and more stable in the first half of the first row transition elements with increasing atomic number?

Q 37.

Although +3 is the characteristic oxidation state for lanthanoids but cerium
also shows +4 oxidation state because  
(a) it has variable ionization enthalpy
(b) it has a tendency to attain noble gas configuration
(c) it has a tendency to attain f ° configuration
(d) it resembles  Pb4+

Q 38.

The second and third rows of tfansition elements resemble each other much more than they resemble the first row. Explain why?

Q 39.

The halides of transition elements become more covalent with increasing oxidation state of the metal. Why?

Q 40.

Write down the electronic configuration of (i) Cr3+ (ii) Pm3+ (iii) Cu+ (iv) Ce4+(v) Co2+ (vi) Lu2+(vii) Mn2+ (viii) Th4+.

Q 41.

How is the variability in oxidation states of transition metals different from that of the non transition metals? Illustrate with examples.

Q 42.

How would you account for the following:
(i) Of the d4 species, Cr2+ is strongly reducing while manganese (III) is strongly oxidizing.
(ii) Cobalt (II) is stable in aqueous solution but in the presence of complexing reagents it is easily oxidised.
(iii) The d1  configuration is very unstable in ions.

Q 43.

Transition elements show magnetic moment due to spin and orbital motion of electrons. Which of the following metallic ions have almost same spin only magnetic moment?
(a) Co2+ (b) Cr2+ (c) Mn2+ (d)  Cr3+

Q 44.

Out of Cu2Cl2  and CuCl2, which is more stable and why?

Q 45.

Explain why Cu+ ion is not stable in aqueous solutions?

Q 46.

Name the oxometal anions of the first series of the transition metals in which the metal exhibits the oxidation state equal to its group number.

Q 47.

Match the properties given in Column I with the metals given in Column II.
ncert-exemplar-problems-class-12-chemistry-d-f-block-elements-24

Q 48.

Assertion (A): Actinoids form relatively less stable complexes as compared to lanthanoids.
Reason (R): Actinoids can utilize their 5d orbitals along with 6d orbitals in bonding but lanthanoids do not use their 4f orbital for bonding.

Q 49.

Assertion (A): The highest oxidation state of osmium is +8.
Reason (R): Osmium is a 5d-block element.

Q 50.

Identify A to E and expain reaction involves
ncert-exemplar-problems-class-12-chemistry-d-f-block-elements-31