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NCERT Solutions for Class 12 Chemistry Chemistry I Chapter 8 The D-And-f-Block Elements

NCERT Solution For Class 12 Chemistry Chemistry I

The D-And-f-Block Elements Here is the CBSE Chemistry Chapter 8 for Class 12 students. Summary and detailed explanation of the lesson, including the definitions of difficult words. All of the exercises and questions and answers from the lesson's back end have been completed. NCERT Solutions for Class 12 Chemistry The D-And-f-Block Elements Chapter 8 NCERT Solutions for Class 12 Chemistry The D-And-f-Block Elements Chapter 8 The following is a summary in Hindi and English for the academic year 2024-25. You can save these solutions to your computer or use the Class 12 Chemistry.

Question 1

Example	Magnetic Moment (BM)
K₄[Mn(CN)₆]	2.2
[Fe(H₂O)₆]²⁺	5.3
K₃ [Mn Cl₄]	5.9

_{$bold E subscript bold M to the power of bold 2 bold plus end exponent bold divided by bold M end subscript superscript bold 0$}	Cr	Mn	Fe	Co	Ni	Cu
	-0.91	-1.18	-0.44	-0.28	-0.25	-0.34

Catalyst	Process
(A)TiCl3	(i) Wacker Process
(B) PdCl₂	(ii) Ziegler -Natta
(C) CuCl₂	(iii) Contact process
(D) V₂O₅	(iv)Deacon's process

NCERT Solutions for Class 12 Chemistry Chemistry I Chapter 8 The D-And-f-Block Elements

NCERT Solution For Class 12 Chemistry Chemistry I

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

In the series Sc (Z = 21) to Zn(Z = 30), the enthalpy of atomisation of zinc is the lowest i.e., 26, kJ mol. Why?

The E° (M2+/M) value for copper is positive (+ 0.34 V). What is possibility the reason for this?

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

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

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

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

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

Actinoid contraction is greater from element to element than lanthanoid contraction. Why?

On what ground can you say that scandium (Z = 21) is a transition element but zinc (Z = 30) is not?

The outer electronic configuration of copper is 3d10 4s1, yet it is considered transition element. Why?

Why the melting points of transition elements are high?

Why Zn, Cd and Hg are not regarded as transition elements?

Name the first element of 3rd transition series.

Though copper, silver and gold have completely filled sets of d-orbitals yet they are considered as transition metals. Why?

Why are transition elements so named?

Why are transition elements known as d-block elements?

Write the general electronic configuration of d-block elements.

Why do some exceptions to the general electronic configuration of d-block elements exists?

Why Cr and Cu show exceptional configuration?

Why Pd is not called a transition elements?

Why is the density of Zn lower than that of Cu?

Atomic radius in a transition series does not vary much while that of s and p-block does. Why?

Explain why iron is a transition element but sodium is not?

Why do the transition elements exhibit higher enthalpies of atomisation?

Why is the enthalpy of atomisation increases upto the middle of the transition series and then decreases?

Why are Zn, Cd and Hg softer and volatile metals?

Why does Zr and Hf exhibit similar properties?

Why is the following electronic configuration not correct for the ground state of Mo atom? (at. no. = 42).1s2 2s2 2p6 3s23p63d10 4s2 4p6 4d4 5s2.

Name a transition element which does not exhibit variable oxidation states.

Which element shows the highest oxidation state among the d-block elements?

What is the reason of transition elements to exhibit variable oxidation states?

Out of V and Mn which exhibits more oxidation states?

What is the most stable oxidation state of Mn (Z = 25)?

Write the highest oxidation state shown by element with atomic number 23.

The electronic configuration of an element is 3d5 4s1. Write its (i) most stable oxidation state and (ii) most oxidising state.

The electronic configuration of an element is 3d5 4s1. Write its (i) most stable oxidation states and (ii) most oxidising oxidation state.

What is the highest oxidation state shown by Cr (Z = 24)?

Why are Cr2+ reducing and Mn3+ oxidising when both have d4 configurations?

The E° value of Zn2+/Zn and Mn2+/Mn are quite low. Why?

Why V and Mn has E° value more than E° value of Cr?

What may be the stable oxidation state of the transition elements with the following d-electron configurations in the ground state of their atoms 3d3, 3d5, 3d8 and 3d4?

Transition metals tend to be less reactive. Explain

Compare qualitatively the first and second ionisation potentials of copper and zinc. Explain the above observation.

What does the E° value of M3+/M2+ show for Mn3+ and Co3+ (+ 1.57 and 1.97 V respectively)?

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

Give a reaction to show that Cr2+ acts as a reducing agent.

Why is the E° value for Mn3+/Mn2+ higher than that of Cr3+/ Cr2+ (or Fe3+/Fe2+)?

How would you account for the increasing oxidising power in the series VO2+< Cr2O72– < MnO4–?

The ionisation enthalpies of Cr and Cu are larger than their neighbours. Why?

The first ionisation energies of third transition series is higher than those of first and second transition series. Why?

For the first row transition metals the E° values are:E° V Cr Mn Fe Co Mc Cu(M2+/M) –1.18 –0.91 –1.18 –0.44 –0.28 –0.25 +0.34Explain the irregularity in the above values.

Why is the E° value for the Mn3+/Mn2+ couple much more positive than that for Cr3+/Cr2+ or Fe3+/Fe2+? Explain.

What would be the nature of copper(I) oxide?

Calculate the magnetic moment of a divalent ion in aqueous solution its atomic number is 25.

Give the formula for finding out the magnetic moment of an atom.

What is the unit of magnetic moment (μ)?

The d-electron configuration of Co2+ and Cu2+ is d7 and d9 respectively. Which one of these ions will be more paramagnetic?

The d-electron configuration of Mn2+ and Ti2+ is d5 and d2 respectively. Which one of these ions will be more paramagnetic?

Why is bivalent Ti2+ ion paramagnetic in nature?

Why do transition elements exhibit paramagnetism?

Why does Mn(II) ion show maximum paramagnetic character amongst bivalent ions of first transition series?

Calculate the magnetic moment of Fe3+ ion (at. no. of Fe = 26).

Why Zn2+ salts are white while Ni2+ salts are blue?

Why Zn2+ salts are white while Cu2+ salts are blue?

[Ti(H2O)6]3+ is coloured while [Sc(H2O)6]3+ is colourless. Explain.

Giving reasons indicate which one of the following would be coloured?Cu+, V2+, Sc3+ Ni2+ (At. No., Cu = 29, V = 23, Sc = 21, Ni = 28)

Why Cd2+ salts are white?

Cu+ is colourless but Cu2+ is coloured. Why?

Which of the following do you expect to be coloured and why? Cr+, Cu+?

Why is copper sulphate pentahydrate coloured?

Transition metals usually form coloured ions, why?

Zn, Cd, Hg compounds are usually white. Explain.

Give one example of any compound in which the oxidation state of Ni is zero.

Why does V2O5 act as catalyst?

Transition metals form a large number of interstitial compounds. Explain.

What is an alloy? Name the two types of alloy formed by transition elements. Give one example of a solid solution in relation to a smooth alloy.

Give two properties in which interstitial compounds differ from its elements.

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

The E° (M²⁺/M) value for copper is positive (+ 0.34 V). What is possibility the reason for this?

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

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

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

The outer electronic configuration of copper is 3d¹⁰ 4s¹, yet it is considered transition element. Why?

Why is the following electronic configuration not correct for the ground state of Mo atom? (at. no. = 42).
1s² 2s² 2p⁶ 3s²3p⁶3d¹⁰ 4s² 4p⁶ 4d⁴ 5s².

The electronic configuration of an element is 3d⁵ 4s¹. Write its (i) most stable oxidation state and (ii) most oxidising state.

The electronic configuration of an element is 3d⁵ 4s¹. Write its (i) most stable oxidation states and (ii) most oxidising oxidation state.

Why are Cr²⁺ reducing and Mn³⁺ oxidising when both have d⁴ configurations?

The E° value of Zn²⁺/Zn and Mn²⁺/Mn are quite low. Why?

What may be the stable oxidation state of the transition elements with the following d-electron configurations in the ground state of their atoms 3d³, 3d⁵, 3d⁸ and 3d⁴?

What does the E° value of M³⁺/M²⁺ show for Mn³⁺and Co³⁺ (+ 1.57 and 1.97 V respectively)?

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

Give a reaction to show that Cr²⁺ acts as a reducing agent.

Why is the E° value for Mn³⁺/Mn²⁺ higher than that of Cr³⁺/ Cr²⁺ (or Fe³⁺/Fe²⁺)?

How would you account for the increasing oxidising power in the series VO₂⁺< Cr₂O₇^2– < MnO₄–?

For the first row transition metals the E° values are:
E° V Cr Mn Fe Co Mc Cu
(M²⁺/M) –1.18 –0.91 –1.18 –0.44 –0.28 –0.25 +0.34
Explain the irregularity in the above values.

Why is the E° value for the Mn³⁺/Mn²⁺ couple much more positive than that for Cr³⁺/Cr²⁺ or Fe³⁺/Fe²⁺? Explain.

The d-electron configuration of Co²⁺ and Cu²⁺ is d⁷ and d⁹ respectively. Which one of these ions will be more paramagnetic?

The d-electron configuration of Mn²⁺ and Ti²⁺ is d⁵ and d² respectively. Which one of these ions will be more paramagnetic?

Why is bivalent Ti²⁺ion paramagnetic in nature?

Calculate the magnetic moment of Fe³⁺ ion (at. no. of Fe = 26).

Why Zn²⁺ salts are white while Ni²⁺ salts are blue?

Why Zn²⁺ salts are white while Cu²⁺ salts are blue?

[Ti(H₂O)₆]³⁺ is coloured while [Sc(H₂O)₆]³⁺ is colourless. Explain.

Giving reasons indicate which one of the following would be coloured?
Cu⁺, V²⁺, Sc³⁺ Ni²⁺ (At. No., Cu = 29, V = 23, Sc = 21, Ni = 28)

Why Cd²⁺ salts are white?

Cu⁺ is colourless but Cu²⁺ is coloured. Why?

Which of the following do you expect to be coloured and why? Cr⁺, Cu⁺?

Why does V₂O₅ act as catalyst?

Cu²⁺ is more stable than Cu⁺, Explain.

Why is hydrochloric acid not used to acidify a permanganate solution in volumetric estimation of Fe²⁺ or C₂O₄^2–?

Give one reaction in which neutral solution of KMnO₄ acts as an oxidizing agent.

What happens when SO₂ gas is passed through an acidified K₂Cr₂O₇ solution?

Why is K₂Cr₂O₇ generally preferred over Na₂Cr₂O₇ in volumetric analysis although both are oxidising agents?

Write a balanced equation for the reaction of K₂Cr₂O₇ with ferrous sulphate solution in presence of dil. H₂SO₄.

What is the range of E° value of lanthanoids for Ln³⁺/Ln?

Why Sm²⁺, Eu²⁺ and Yb²⁺ ions in solutions are good reducing agents but an aqueous solution of Ce⁴⁺ is a good oxidizing agent?

What is the effect of increasing pH in K₂Cr₂O₇, solution?

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

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

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

Explain giving reason:
Transition metals and many of their compounds show paramagnetic behaviour.

Explain giving reason:
The enthalpies of atomisation of the transition metals are high.

Explain giving reason:
The transition metals generally form coloured compounds.

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

Describe the oxidising action of potassium dichromate and write the ionic equations for its reaction with:
(a) iodide (b) iron (II) solution and (c) H₂S.

Describe the preparation of potassium permanganate. How does the acidified permanganate solution reacts with (a) iron (II) ions (b) SO₂ and (c) oxalic acid ? Write the ionic equations for the reactions.

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

Compare the chemistry of actinides with that of the lanthanoids with special reference to:
(i) electronic configuration, (ii) atomic and ionic sizes, (iii) oxidation state (iv) chemical reactivity.

Give reasons for the following:
Transition metals have high enthalpies of atomisation.