NCERT Exemplar solutions for Chemistry [English] Class 12 chapter 8 - The d-and f-Block Elements [Latest edition]

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

The electronic configuration of \[\ce{Cu(II)}\] is 3d⁹ whereas that of \[\ce{Cu(I)}\] is 3d¹⁰. Which of the following is correct?

Metallic radii of some transition elements are given below. Which of these elements will have highest density?

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

On addition of small amount of \[\ce{KMnO4}\] to concentrated \[\ce{H2SO4}\], a green oily compound is obtained which is highly explosive in nature. Identify the compound from the following.

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

Which of the following oxidation state is common for all lanthanoids?

Which of the following reactions are disproportionation reactions?

(a) \[\ce{Cu^{+} -> Cu^{2+} + Cu}\]

(b) \[\ce{3MnO^{-}4 + 4H^{+} -> 2MnO^{-}4 + MnO2 + 2H2O}\]

(c) \[\ce{2KMnO4 -> K2MnO4 + MnO2 + O2}\]

(d) \[\ce{2MnO^{-}4 + 3Mn^{2+} + 2H2O -> 5MnO2 + 4H^{+}}\]

When \[\ce{KMnO4}\] solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time because ______.

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

\[\ce{KMnO4}\] acts as an oxidising agent in acidic medium. The number of moles of \[\ce{KMnO4}\] that will be needed to react with one mole of sulphide ions in acidic solution is ______.

Which of the following is amphoteric oxide?

\[\ce{Mn2O7, CrO3, Cr2O3, CrO, V2O5, V2O4}\]

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

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?

The magnetic moment is associated with its spin angular momentum and orbital angular momentum. Spin only magnetic moment value of \[\ce{Cr^{3+}}\] ion is ______.

\[\ce{KMnO4}\] acts as an oxidising agent in alkaline medium. When alkaline \[\ce{KMnO4}\]  is treated with \[\ce{KI}\], iodide ion is oxidised to ______.

Which of the following statements is not correct?

When acidified \[\ce{K2Cr2O7}\] solution is added to \[\ce{Sn^{2+}}\] salts then \[\ce{Sn^{2+}}\] changes to ______.

Highest oxidation state of manganese in fluoride is \[\ce{+4 (MnF4)}\] but highest oxidation state in oxides is \[\ce{+7 (Mn2O7)}\] because ______.

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

Why is \[\ce{HCl}\] not used to make the medium acidic in oxidation reactions of \[\ce{KMnO4}\] in acidic medium?

Generally transition elements and their salts are coloured due to the presence of unpaired electrons in metal ions. Which of the following compounds are coloured?

(i) \[\ce{KMnO4}\]

(ii) \[\ce{Ce(SO4)2}\]

(iii) \[\ce{TiCl}\]

(iv) \[\ce{Cu2 Cl2}\]

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?

(i) \[\ce{Co^{2+}}\]

(ii) \[\ce{Cr^{2+}}\]

(iii) \[\ce{Mn^{2+}}\]

(iv) \[\ce{Cr^{3+}}\]

In the form of dichromate, \[\ce{Cr (VI)}\] is a strong oxidising agent in acidic medium but \[\ce{Mo (VI)}\] in \[\ce{MoO3}\] \[\ce{and W (VI)}\] in \[\ce{WO3}\] are not because:

(i) \[\ce{Cr(VI)}\] is more stable than \[\ce{Mo(VI)}\] and  \[\ce{and W(VI)}\].

(ii) \[\ce{Mo(VI)}\] and \[\ce{and W(VI)}\] are more stable than  \[\ce{Cr(VI)}\].

(iii) Higher oxidation states of heavier members of group-6 of transition series are more stable.

(iv) Lower oxidation states of heavier members of group-6 of transition series are more stable.

Which of the following actinoids show oxidation states upto +7?

(i) Am

(ii) Pu

(iii) U

(iv) Np

General electronic configuration of actinoids is `(n-2)f^(1-14)(n - 1)d^(0-2)ns^2`.Which of the following actinoids have one electron in 6d orbital?

(i) U (Atomic no. 92)

(ii) Np (Atomic no.93)

(iii) Pu (Atomic no. 94)

(iv) Am (Atomic no. 95)

Which of the following lanthanoids show +2 oxidation state besides the characteristic oxidation state +3 of lanthanoids?

(i) \[\ce{Ce}\]

(ii) \[\ce{Eu}\]

(iii) \[\ce{Yb}\]

(iv) \[\ce{Ho}\]

Which of the following ions show higher spin only magnetic moment value?

(i) \[\ce{Ti^3+}\]

(ii) \[\ce{Mn2+}\]

(iii) \[\ce{Fe2+}\]

(iv) \[\ce{Co3+}\]

Transition elements form binary compounds with halogens. Which of the following elements will form \[\ce{MF3}\] type compounds?

(i) \[\ce{Cr}\]

(ii) \[\ce{Co}\]

(iii) \[\ce{Cu}\]

(iv) \[\ce{Ni}\]

Which of the following will not act as oxidising agents?

(i) \[\ce{CrO3}\]

(ii) \[\ce{MoO3}\]

(iii) \[\ce{WO3}\]

(iv) \[\ce{CrO^{2-}4}\]

Although +3 is the characteristic oxidation state for lanthanoids but cerium also shows +4 oxidation state because:

(i) it has variable ionisation enthalpy

(ii) it has a tendency to attain noble gas configuration

(iii) it has a tendency to attain f 0 configuration

(iv) it resembles Pb⁴⁺ 

Why does copper not replace hydrogen from acids?

Why E^Θ values for Mn, Ni and Zn are more negative than expected?

Why first ionisation enthalpy of Cr is lower than that of Zn?

Transition elements show high melting points. Why?

When \[\ce{Cu^2+}\] ion is treated with \[\ce{KI}\], a white precipitate is formed. Explain the reaction with the help of chemical equation.

Out of \[\ce{Cu2Cl2}\] and \[\ce{CuCl2}\], which is more stable and why?

When a brown compound of manganese (A) is treated with \[\ce{HCl}\] it gives a gas (B). The gas taken in excess, reacts with \[\ce{NH3}\] to give an explosive compound (C). Identify compounds A, B and C.

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

Although \[\ce{Cr^3+}\] and \[\ce{Co^2+}\] ions have same number of unpaired electrons but the magnetic moment of \[\ce{Cr^3+}\] is 3.87 B.M. and that of \[\ce{Co^2+}\] is 4.87 B.M. Why?

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

Although Zr belongs to 4d and Hf belongs to 5d transition series but it is quite difficult to separate them. Why?

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

Explain why does colour of \[\ce{KMNO4}\] disappear when oxalic acid is added to its solution in acidic medium.

When orange solution containing \[\ce{Cr2O^{2-}7}\] ion is treated with an alkali, a yellow solution is formed and when \[\ce{H^+}\] ions are added to yellow solution, an orange solution is obtained. Explain why does this happen?

A solution of \[\ce{KMnO4}\] 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?

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

E^Θ of Cu is + 0.34V while that of Zn is – 0.76V. Explain.

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

While filling up of electrons in the atomic orbitals, the 4s orbital is filled before the 3d orbital but reverse happens during the ionisation of the atom. Explain why?

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

Match the catalysts given in Column I with the processes given in Column II.

Match the compounds/elements given in Column I with uses given in Column II.

Match the properties given in Column I with the metals given in Column II.

Match the statements given in Column I with the oxidation states given in Column II.

Match the solutions given in Column I and the colours given in Column II.

Match the property given in Column I with the element given in Column II.

Match the properties given in Column I with the metals given in Column II.

Assertion: \[\ce{Cu^2+}\] iodide is not known.

Reason: \[\ce{Cu^2+}\] oxidises \[\ce{I^-}\] to iodine.

Assertion: Separation of \[\ce{Zr}\] and \[\ce{Hf}\] is difficult.

Reason: Because \[\ce{Zr}\] and \[\ce{Hf}\] lie in the same group of the periodic table.

Assertion: Actinoids form relatively less stable complexes as compared to lanthanoids.

Reason: Actinoids can utilise their 5f orbitals along with 6d orbitals in bonding but lanthanoids do not use their 4f orbital for bonding.

Assertion: \[\ce{Cu}\] cannot liberate hydrogen from acids.

Reason: Because it has positive electrode potential.

Assertion: The highest oxidation state of osmium is +8.

Reason: Osmium is a 5d-block element.

Identify A to E and also explain the reactions involved.

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 crystallised 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.

When an oxide of manganese (A) is fused with KOH in the presence of an oxidising agent and dissolved in water, it gives a dark green solution of compound (B). Compound (B) disproportionates in neutral or acidic solution to give purple compound (C). An alkaline solution of compound (C) oxidises potassium iodide solution to a compound (D) and compound (A) is also formed. Identify compounds A to D and also explain the reactions involved.

On the basis of Lanthanoid contraction, explain the following:

Nature of bonding in \[\ce{La2O3}\] and \[\ce{Lu2O3}\] .

On the basis of Lanthanoid contraction, explain the following:

Trends in the stability of oxo salts of lanthanoids from \[\ce{La}\] to \[\ce{Lu}\].

On the basis of Lanthanoid contraction, explain the following:

Stability of the complexes of lanthanoids.

On the basis of Lanthanoid contraction, explain the following:

Radii of 4d and 5d block elements.

On the basis of Lanthanoid contraction, explain the following:

Trends in acidic character of lanthanoid oxides.

Answer the following question:

Which element of the first transition series has highest second ionisation enthalpy?

Answer the following question:

Which element of the first transition series has highest third ionisation enthalpy?

Answer the following question:

Which element of the first transition series has lowest enthalpy of atomisation?

Identify the metal and justify your answer.

Carbonyl \[\ce{M(CO)5}\]

Identify the metal and justify your answer.

\[\ce{MO3F}\]

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.

Transition metals can act as catalysts because these can change their oxidation state. How does \[\ce{Fe(III)}\] catalyse the reaction between iodide and persulphate ions?

Mention any three processes where transition metals act as catalysts.

A violet compound of manganese (A) decomposes on heating to liberate oxygen and compounds (B) and (C) of manganese are formed. Compound (C) reacts with KOH in the presence of potassium nitrate to give compound (B). On heating compound (C) with conc. \[\ce{H2SO4}\] and \[\ce{NaCl}\], chlorine gas is liberated and a compound (D) of manganese along with other products is formed. Identify compounds A to D and also explain the reactions involved.