For M2+/M and M3+/M2+ systems, the E⊖& | Class 12 Chemistry Chapter The d-and f-Block Elements, The d-and f-Block Elements NCERT Solutions

Welcome to the NCERT Solutions for Class 12 Chemistry - Chapter The d-and f-Block Elements. This page offers a step-by-step solution to the specific question from Exercise 2, Question 17: . With detailed answers and explanations for each chapter, students can strengthen their understanding and prepare confidently for exams. Ideal for CBSE and other board students, this resource will simplify your study experience.

Question 17:

For M²⁺/M and M³⁺/M²⁺ systems, the E^⊖ 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.

Answer:

(i) The E^⊖ value for Fe³⁺/Fe²⁺ is higher than that for Cr³⁺/Cr²⁺and lower than that for Mn³⁺/Mn²⁺. So, the reduction of Fe³⁺to Fe²⁺is easier than the reduction of Mn³⁺to Mn²⁺, but not as easy as the reduction of Cr³⁺ to Cr²⁺. Hence, Fe³⁺is more stable than Mn³⁺, but less stable than Cr³⁺. These metal ions can be arranged in the increasing order of their stability as: Mn³⁺< Fe³⁺< Cr³⁺

(ii) The reduction potentials for the given pairs increase in the following order.

Mn²⁺ / Mn < Cr²⁺ / Cr < Fe²⁺ /Fe

So, the oxidation of Fe to Fe²⁺is not as easy as the oxidation of Cr to Cr²⁺and the oxidation of Mn to Mn²⁺. Thus, these metals can be arranged in the increasing order of their ability to get oxidised as: Fe < Cr < Mn value for Fe3+/ Fe2+ is higher than that for Cr3+/Cr2+and lower than that for Mn3+/Mn2+. So, the reduction of Fe3+to Fe2+is easier than the reduction of Mn3+to Mn2+, but not as easy as the reduction of Cr3+ to Cr2+. Hence, Fe3+is more stable than Mn3+, but less stable than Cr3+. These metal ions can be arranged in the increasing order of their stability as: Mn3+< Fe3+< Cr3+ (ii) The reduction potentials for the given pairs increase in the following order. Mn2+ / Mn < Cr2+ / Cr < Fe2+ /Fe So, the oxidation of Fe to Fe2+is not as easy as the oxidation of Cr to Cr2+and the oxidation of Mn to Mn2+. Thus, these metals can be arranged in the increasing order of their ability to get oxidised as: Fe < Cr < Mn

Other Questions of Chapter The d-and f-Block Elements

What are the different oxidation states exhibited by the lanthanoids?

Describe the oxidising action of potassium dichromate and write the ionicequations for its reaction with:

(i) iodide

(ii) iron

(II) solution and

(iii) H₂S

How would you account for the following:

(i) Of the d⁴ species, Cr²⁺ is strongly reducing while manganese (III) is strongly oxidising.

(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.

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.

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

Calculate the 'spin only' magnetic moment of M²⁺_(aq) ion (Z = 27).

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.

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?

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

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

Popular questions of class 12 Chemistry

How the following conversions can be carried out?

(i) Propene to propan-1-ol

(ii) Ethanol to but-1-yne

(iii) 1-Bromopropane to 2-bromopropane

(iv) Toluene to benzyl alcohol

(v) Benzene to 4-bromonitrobenzene

(vi) Benzyl alcohol to 2-phenylethanoic acid

(vii) Ethanol to propanenitrile

(viii) Aniline to chlorobenzene

(ix) 2-Chlorobutane to 3, 4-dimethylhexane

(x) 2-Methyl-1-propene to 2-chloro-2-methylpropane

(xi) Ethyl chloride to propanoic acid

(xii) But-1-ene to n-butyliodide

(xiii) 2-Chloropropane to 1-propanol

(xiv) Isopropyl alcohol to iodoform

(xv) Chlorobenzene to p-nitrophenol

(xvi) 2-Bromopropane to 1-bromopropane

(xvii) Chloroethane to butane

(xviii) Benzene to diphenyl

(xix) tert-Butyl bromide to isobutyl bromide

(xx) Aniline to phenylisocyanide

Give simple chemical tests to distinguish between the following pairs of compounds.

(i) Propanal and Propanone

(ii) Acetophenone and Benzophenone

(iii) Phenol and Benzoic acid

(iv) Benzoic acid and Ethyl benzoate

(v) Pentan-2-one and Pentan-3-one

(vi) Benzaldehyde and Acetophenone

(vii) Ethanal and Propanal

A 5% solution (by mass) of cane sugar in water has freezing point of 271 K. Calculate the freezing point of 5% glucose in water if freezing point of pure water is 273.15 K.

A solution of glucose in water is labelled as 10% w/w, what would be the molality and mole fraction of each component in the solution? If the density of solution is 1.2 g mL^-1, then what shall be the molarity of the solution?

Henry's law constant for CO₂ in water is 1.67 x 10⁸Pa at 298 K. Calculate the quantity of CO₂in 500 mL of soda water when packed under 2.5 atm CO₂pressure at 298 K.

Calculate the mass of a non-volatile solute (molar mass 40 g mol^-1) which should be dissolved in 114 g octane to reduce its vapour pressure to 80%.

The vapour pressure of pure liquids A and B are 450 and 700 mm Hg respectively, at 350 K. Find out the composition of the liquid mixture if total vapour pressure is 600 mm Hg. Also find the composition of the vapour phase.

Calculate the mole fraction of benzene in solution containing 30% by mass in carbon tetrachloride.

How many mL of 0.1 M HCl are required to react completely with 1 g mixture of Na₂CO₃ and NaHCO₃ containing equimolar amounts of both?

If NaCl is doped with 10^-3mol % of SrCl₂, what is the concentration of cation vacancies?

Recently Viewed Questions of Class 12 Chemistry

Henry's law constant for CO₂ in water is 1.67 x 10⁸Pa at 298 K. Calculate the quantity of CO₂in 500 mL of soda water when packed under 2.5 atm CO₂pressure at 298 K.

What are nucleic acids? Mention their two important functions.

The reaction between A and B is first order with respect to A and zero order with respect to B. Fill in the blanks in the following table:

Experiment	A/ mol L^{- 1}	B/ mol L^{- 1}	Initial rate/mol L^{- 1} min^{- 1}
I	0.1	0.1	2.0 × 10^{- 2}
II	--	0.2	4.0 × 10^{- 2}
III	0.4	0.4	--
IV	--	0.2	2.0 × 10^{- 2}

Mention the conditions required to maximise the yield of ammonia.

Ionic solids conduct electricity in molten state but not in solid state. Explain.

What type of solids are electrical conductors, malleable and ductile?

Write the structure of the major organic product in each of the following reactions:

Ferric oxide crystallises in a hexagonal close-packed array of oxide ions with two out of every three octahedral holes occupied by ferric ions. Derive the formula of the ferric oxide.

How will you bring about the following conversions?

(i) Ethanol to but-1-yne

(ii) Ethane to bromoethene

(iii) Propene to 1-nitropropane

(iv) Toluene to benzyl alcohol

(v) Propene to propyne

(vi) Ethanol to ethyl fluoride

(vii) Bromomethane to propanone

(viii) But-1-ene to but-2-ene

(ix) 1-Chlorobutane to n-octane

(x) Benzene to biphenyl.

What is meant by hydroboration-oxidation reaction? Illustrate it with an example.

Study Tips for Answering NCERT Questions:

NCERT questions are designed to test your understanding of the concepts and theories discussed in the chapter. Here are some tips to help you answer NCERT questions effectively:

Read the question carefully and focus on the core concept being asked.
Reference examples and data from the chapter when answering questions about The d-and f-Block Elements.
Review previous year question papers to get an idea of how such questions may be framed in exams.
Practice answering questions within the time limit to improve your speed and accuracy.
Discuss your answers with your teachers or peers to get feedback and improve your understanding.

Latest Blog Posts

Stay updated with our latest educational content and study tips

Simple and Compound Interest Formulas with Questions

Interest is one of the most significant ideas in maths and financial calculations. It is very common in banking, loan applications, investments, saving account and competitive exams. Simple Interest and Compound Interest make it easier to find out how much more is earned and/or paid on a principal during the period of time. These Interest … Read more

Spoken English Course Topics for Beginners in 2026

In 2026, students, professionals, and job seekers must have a high level of spoken English. Spoken English is a beginner level course to enhance learners’ communication skills in English, their pronunciation, vocabulary, grammar structure and confidence in speaking English fluently. Today, the emphasis of spoken English courses is placed on actual conversations, everyday speech practice … Read more

Difference Between AI and Machine Learning

Artificial Intelligence (AI) and Machine Learning (ML) are two of the most sought-after technologies in today’s digital era. Although these terms are often used together, they are not the same. Machine Learning is, in fact, a component of Artificial Intelligence that enables systems to learn and enhance on their own, without direct programming. AI is … Read more

Time, Speed and Distance Formulas

Time, Speed, and Distance are some of the most important concepts in mathematics and aptitude. These are the concepts which are used to calculate the speed of an object, time taken for an object to move and the distance traveled during the motion. Questions from this topic are frequently seen in School Tests, Competitive Tests, … Read more

View All Blog Posts