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# NCERT solutions for Class 12 Chemistry chapter 8 - The d-block and f-block Elements

## Chapter 8: The d-block and f-block Elements

#### Chapter 8: The d-block and f-block Elements solutions [Pages 212 - 232]

Q 1 | Page 212

Silver atom has completely filled orbitals (4d10) in its ground state. How can you say that it is a transition element?

Q 2 | Page 215

In the series Sc (= 21) to Zn (= 30), the enthalpy of atomization of zinc is the lowest, i.e., 126 kJ mol−1. Why?

Q 3 | Page 217

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

Q 4 | Page 217

The Eθ(M2+/M) value for copper is positive (+0.34V). What is possibly the reason for this? (Hint: consider its high ΔaHθ and low ΔhydHθ)

Q 5 | Page 219

How would you account for the irregular variation of ionization enthalpies (first and second) in the first series of the transition elements?

Q 6 | Page 220

Why is the highest oxidation state of a metal exhibited in its oxide or fluoride only?

Q 7 | Page 220

Which is a stronger reducing agent Cr2+ or Fe2+ and why?

Q 8 | Page 222

Calculate the ‘spin only’ magnetic moment of M2+(aq) ion (= 27).

Q 9 | Page 224

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

Q 10 | Page 232

How would you account for the following : Actinoid contraction is greater than lanthanoid contraction.

#### Chapter 8: The d-block and f-block Elements solutions [Pages 234 - 236]

Q 1.1 | Page 234

Write down the electronic configuration of Cr3+

Q 1.2 | Page 234

Write down the electronic configuration of Pm3+

Q 1.3 | Page 234

Write down the electronic configuration of Cu+

Q 1.4 | Page 234

Write down the electronic configuration of Ce4+

Q 1.5 | Page 234

Write down the electronic configuration of Co2+

Q 1.6 | Page 234

Write down the electronic configuration of Lu2+

Q 1.7 | Page 234

Write down the electronic configuration of Mn2+

Q 1.8 | Page 234

Write down the electronic configuration of Th4+

Q 2 | Page 234

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

Q 3 | Page 234

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 4 | Page 234

To what extent do the electronic configurations decide the stability of oxidation states in the first series of the transition elements? Illustrate your answer with examples.

Q 5 | Page 234

What may be the stable oxidation state of the transition element with the following electron configurations in the ground state of their atoms : 3d3,3d5, 3d8and 3d4?

Q 6 | Page 234

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 7 | Page 234

Define lanthanoid contraction.

Q 8.1 | Page 234

What are the characteristics of the transition elements and why are they called transition elements?

Q 8.2 | Page 234

Which of the d-block elements may not be regarded as the transition elements?

Q 9 | Page 234

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

Q 10 | Page 234

What are the different oxidation states exhibited by the lanthanoids?

Q 11.1 | Page 234

Explain giving reasons:

Transition metals and many of their compounds show paramagnetic behaviour.

Q 11.2 | Page 234

Why do the transition elements have higher enthalpies of atomisation?

Q 11.3 | Page 234

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

Q 11.4 | Page 234

Explain giving reasons:  Transition metals and their many compounds act as good catalyst.

Q 12 | Page 234

Explain Interstitial compounds

Q 13 | Page 234

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

Q 14 | Page 234

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

Q 15 | Page 234

Describe the oxidising action of potassium dichromate and write the ionic equations for its reaction with: (i) iodide (ii) iron(II) solution and (iii) H2S

Q 16 | Page 235

Describe the preparation of potassium permanganate. How does the acidified permanganate solution react with (i) iron(II) ions (ii) SO2 and (iii) oxalic acid? Write the ionic equations for the reactions.

Q 17 | Page 235

For M2+/M and M3+/M2+ systems, the E^theta values for some metals are as follows:

Cr2+/Cr −0.9V

Cr3/Cr2+ −0.4 V

Mn2+/Mn −1.2V

Mn3+ /Mn2+ +1.5 V

Fe2+ /Fe −0.4V

Fe3+/Fe2+ +0.8 V

Use this data to comment upon:

(i) The stability of Fe3+ in acid solution as compared to that of Cr3+ or Mn3+ and

(ii) The ease with which iron can be oxidised as compared to a similar process for either chromium or manganese metal.

Q 18 | Page 235

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

Q 19 | Page 235

Compare the stability of +2 oxidation state for the elements of the first transition series.

Q 20.1 | Page 235

Compare the chemistry of actinoids with that of the lanthanoids with special reference  to electronic configuration

Q 20.2 | Page 235

Compare the chemistry of actinoids with that of the lanthanoids with special reference to: oxidation state

Q 20.3 | Page 235

Compare the chemistry of actinoids with that of the lanthanoids with special reference to atomic and ionic sizes

Q 20.4 | Page 235

Compare the chemistry of actinoids with that of the lanthanoids with special reference to chemical reactivity.

Q 21.1 | Page 235

How would you account for the following:

Of the d4species, Cr2+ is strongly reducing while manganese(III) is strongly oxidising.

Q 21.2 | Page 235

How would you account for the following:

Cobalt(II) is stable in aqueous solution but in the presence of complexing reagents it is easily oxidised.

Q 21.3 | Page 235

How would you account for the following: The d1 configuration is very unstable in ions.

Q 22 | Page 235

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

Q 23 | Page 235

Which metal in the first series of transition metals exhibits +1 oxidation state most frequently and why?

Q 24 | Page 235

Calculate the number of unpaired electrons in the following gaseous ions: Mn3+, Cr3+, V3+ and Ti3+. Which one of these is the most stable in aqueous solution?

Q 25.1 | Page 235

Give examples and suggest reasons for the following features of the transition metal chemistry:

The lowest oxide of transition metal is basic, the highest is amphoteric/acidic.

Q 25.2 | Page 235

Give examples and suggest reasons for the following features of the transition metal chemistry:

A transition metal exhibits highest oxidation state in oxides and fluorides.

Q 25.3 | Page 235

Give examples and suggest reasons for the following features of the transition metal chemistry:

The highest oxidation state is exhibited in oxoanions of a metal.

Q 26.1 | Page 235

Indicate the steps in the preparation of K2Cr2O7 from chromite ore.

Q 26.2 | Page 235

Indicate the steps in the preparation of:  KMnO4 from pyrolusite ore.

Q 27 | Page 235

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

Q 28 | Page 235

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 29 | Page 235

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 30 | Page 235

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 31 | Page 236

Use Hund’s rule to derive the electronic configuration of Ce3+ ion and calculate its magnetic moment on the basis of ‘spin-only’ formula.

Q 32 | Page 236

Name the members of the lanthanoid series which exhibit +4 oxidation state and those which exhibit +2 oxidation state. Try to correlate this type of behavior with the electronic configurations of these elements.

Q 33.1 | Page 236

Compare the chemistry of the actinoids with that of lanthanoids with reference to chemical reactivity.

Q 33.1 | Page 236

Compare the chemistry of the actinoids with that of lanthanoids with reference to electronic configuration

Q 33.2 | Page 236

Compare the chemistry of the actinoids with that of lanthanoids with reference to oxidation states

Q 34 | Page 236

Write the electronic configurations of the elements with the atomic numbers 61, 91, 101, and 109.

Q 35 | Page 236

Compare 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 36 | Page 236

Write down the number of 3d electrons in each of the following ions:

Ti2+, V2+, Cr3+, Mn2+, Fe2+, Fe3+, CO2+, Ni2+ and Cu2+.

Indicate how would you expect the five 3d orbitals to be occupied for these hydrated ions (octahedral).

Q 37 | Page 236

Comment on the statement that elements of the first transition series possess many properties different from those of heavier transition elements.

Q 38 | Page 236

What can be inferred from the magnetic moment values of the following complex species?

Example Magnetic Moment (BM)

K4[Mn(CN)6] 2.2

[Fe(H2O)6]2+ 5.3

K2[MnCl4] 5.9

## NCERT solutions for Class 12 Chemistry chapter 8 - The d-block and f-block Elements

NCERT solutions for Class 12 Chemistry chapter 8 (The d-block and f-block Elements) include all questions with solution and detail explanation. This will clear students doubts about any question and improve application skills while preparing for board exams. The detailed, step-by-step solutions will help you understand the concepts better and clear your confusions, if any. Shaalaa.com has the CBSE Chemistry Textbook for Class 12 solutions in a manner that help students grasp basic concepts better and faster.

Further, we at shaalaa.com are providing such solutions so that students can prepare for written exams. NCERT textbook solutions can be a core help for self-study and acts as a perfect self-help guidance for students.

Concepts covered in Class 12 Chemistry chapter 8 The d-block and f-block Elements are Position in the Periodic Table, Electronic Configurations of the D-block Elements, General Properties of the Transition Elements (D-block), The Lanthanoids, The Actinoids, Some Important Compounds of Transition Elements - Oxides and Oxoanions of Metals, Some Applications of d and f Block Elements, General Introduction of "D" and "F" Block Element, "D" and "F" Block Elements Numericals.

Using NCERT Class 12 solutions The d-block and f-block Elements exercise by students are an easy way to prepare for the exams, as they involve solutions arranged chapter-wise also page wise. The questions involved in NCERT Solutions are important questions that can be asked in the final exam. Maximum students of CBSE Class 12 prefer NCERT Textbook Solutions to score more in exam.

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