Chapter 8 The D-Block And F-Block Elements

Question 1. Electronic configuration of a transition element X in +3 oxidation state is [Ar]3d$^5$. What is its atomic number?

(i) 25

(ii) 26

(iii) 27

(iv) 24

Question 2. The electronic configuration of Cu(II) is 3d$^9$ whereas that of Cu(I) is 3d$^{10}$. Which of the following is correct?

(i) Cu(II) is more stable

(ii) Cu(II) is less stable

(iii) Cu(I) and Cu(II) are equally stable

(iv) Stability of Cu(I) and Cu(II) depends on nature of copper salts

Question 3. Metallic radii of some transition elements are given below. Which of these elements will have highest density?

(i) Fe

(ii) Ni

(iii) Co

(iv) Cu

Question 4. Generally transition elements form coloured salts due to the presence of unpaired electrons. Which of the following compounds will be coloured in solid state?

(i) $Ag_2SO_4$

(ii) $CuF_2$

(iii) $ZnF_2$

(iv) $Cu_2Cl_2$

Question 5. On addition of small amount of $KMnO_4$ to concentrated $H_2SO_4$, a green oily compound is obtained which is highly explosive in nature. Identify the compound from the following.

(i) $Mn_2O_7$

(ii) $MnO_2$

(iii) $MnSO_4$

(iv) $Mn_2O_3$

Question 6. The magnetic nature of elements depends on the presence of unpaired electrons. Identify the configuration of transition element, which shows highest magnetic moment.

(i) $3d^7$

(ii) $3d^5$

(iii) $3d^8$

(iv) $3d^2$

Question 7. Which of the following oxidation state is common for all lanthanoids?

(i) +2

(ii) +3

(iii) +4

(iv) +5

Question 8. Which of the following reactions are disproportionation reactions?

(a) $Cu^+ \rightarrow Cu^{2+} + Cu$

(b) $3MnO_4^{–} + 4H^+ \rightarrow 2MnO_4^{–} + MnO_2 + 2H_2O$

(c) $2KMnO_4 \rightarrow K_2MnO_4 + MnO_2 + O_2$

(d) $2MnO_4^{–} + 3Mn^{2+} + 2H_2O \rightarrow 5MnO_2 + 4H^+$

(i) a, b

(ii) a, b, c

(iii) b, c, d

(iv) a, d

Question 9. When $KMnO_4$ solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time because

(i) $CO_2$ is formed as the product.

(ii) Reaction is exothermic.

(iii) $MnO_4^–$ catalyses the reaction.

(iv) $Mn^{2+}$ acts as autocatalyst.

Question 10. There are 14 elements in actinoid series. Which of the following elements does not belong to this series?

(i) U

(ii) Np

(iii) Tm

(iv) Fm

Question 11. $KMnO_4$ acts as an oxidising agent in acidic medium. The number of moles of $KMnO_4$ that will be needed to react with one mole of sulphide ions in acidic solution is

(i) $\frac{2}{5}$

(ii) $\frac{3}{5}$

(iii) $\frac{4}{5}$

(iv) $\frac{1}{5}$

Question 12. Which of the following is amphoteric oxide? $Mn_2O_7, CrO_3, Cr_2O_3, CrO, V_2O_5, V_2O_4$

(i) $V_2O_5, Cr_2O_3$

(ii) $Mn_2O_7, CrO_3$

(iii) $CrO, V_2O_5$

(iv) $V_2O_5, V_2O_4$

Question 13. Gadolinium belongs to 4f series. It’s atomic number is 64. Which of the following is the correct electronic configuration of gadolinium?

(i) [Xe] $4f^7 5d^1 6s^2$

(ii) [Xe] $4f^6 5d^2 6s^2$

(iii) [Xe] $4f^8 6d^2$

(iv) [Xe] $4f^9 5s^1$

Question 14. 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?

(i) They have high melting points in comparison to pure metals.

(ii) They are very hard.

(iii) They retain metallic conductivity.

(iv) They are chemically very reactive.

Question 15. The magnetic moment is associated with its spin angular momentum and orbital angular momentum. Spin only magnetic moment value of $Cr^{3+}$ ion is __________.

(i) 2.87 B.M.

(ii) 3.87 B.M.

(iii) 3.47 B.M.

(iv) 3.57 B.M.

Question 16. $KMnO_4$ acts as an oxidising agent in alkaline medium. When alkaline $KMnO_4$ is treated with KI, iodide ion is oxidised to ____________.

(i) $I_2$

(ii) $IO^–$

(iii) $IO_3^–$

(iv) $IO_4^–$

Question 17. Which of the following statements is not correct?

(i) Copper liberates hydrogen from acids.

(ii) In its higher oxidation states, manganese forms stable compounds with oxygen and fluorine.

(iii) $Mn^{3+}$ and $Co^{3+}$ are oxidising agents in aqueous solution.

(iv) $Ti^{2+}$ and $Cr^{2+}$ are reducing agents in aqueous solution.

Question 18. When acidified $K_2Cr_2O_7$ solution is added to $Sn^{2+}$ salts then $Sn^{2+}$ changes to

(i) Sn

(ii) $Sn^{3+}$

(iii) $Sn^{4+}$

(iv) $Sn^+$

Question 19. Highest oxidation state of manganese in fluoride is +4 ($MnF_4$) but highest oxidation state in oxides is +7 ($Mn_2O_7$) because ____________.

(i) fluorine is more electronegative than oxygen.

(ii) fluorine does not possess d-orbitals.

(iii) fluorine stabilises lower oxidation state.

(iv) in covalent compounds fluorine can form single bond only while oxygen forms double bond.

Question 20. Although Zirconium belongs to 4d transition series and Hafnium to 5d transition series even then they show similar physical and chemical properties because___________.

(i) both belong to d-block.

(ii) both have same number of electrons.

(iii) both have similar atomic radius.

(iv) both belong to the same group of the periodic table.

Question 21. Why is HCl not used to make the medium acidic in oxidation reactions of $KMnO_4$ in acidic medium?

(i) Both HCl and $KMnO_4$ act as oxidising agents.

(ii) $KMnO_4$ oxidises HCl into $Cl_2$ which is also an oxidising agent.

(iii) $KMnO_4$ is a weaker oxidising agent than HCl.

(iv) $KMnO_4$ acts as a reducing agent in the presence of HCl.

Question 22. 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) $KMnO_4$

(ii) $Ce(SO_4)_2$

(iii) $TiCl_4$

(iv) $Cu_2Cl_2$

Question 23. 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) $Co^{2+}$

(ii) $Cr^{2+}$

(iii) $Mn^{2+}$

(iv) $Cr^{3+}$

Question 24. In the form of dichromate, Cr (VI) is a strong oxidising agent in acidic medium but Mo (VI) in $MoO_3$ and W (VI) in $WO_3$ are not because __________.

(i) Cr (VI) is more stable than Mo(VI) and W(VI).

(ii) Mo(VI) and W(VI) are more stable than 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.

Question 25. Which of the following actinoids show oxidation states upto +7?

(i) Am

(ii) Pu

(iii) U

(iv) Np

Question 26. General electronic configuration of actionoids 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)

Question 27. Which of the following lanthanoids show +2 oxidation state besides the characteristic oxidation state +3 of lanthanoids?

(i) Ce

(ii) Eu

(iii) Yb

(iv) Ho

Question 28. Which of the following ions show higher spin only magnetic moment value?

(i) $Ti^{3+}$

(ii) $Mn^{2+}$

(iii) $Fe^{2+}$

(iv) $Co^{3+}$

Question 29. Transition elements form binary compounds with halogens. Which of the following elements will form $MF_3$ type compounds?

(i) Cr

(ii) Co

(iii) Cu

(iv) Ni

Question 30. Which of the following will not act as oxidising agents?

(i) $CrO_3$

(ii) $MoO_3$

(iii) $WO_3$

(iv) $CrO_4^{2–}$

Question 31. 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 $Pb^{4+}$

Question 32. Why does copper not replace hydrogen from acids?

Question 33. Why $E^{\ominus}$ values for Mn, Ni and Zn are more negative than expected?

Question 34. Why first ionisation enthalpy of Cr is lower than that of Zn ?

Question 35. Transition elements show high melting points. Why?

Question 36. When $Cu^{2+}$ ion is treated with KI, a white precipitate is formed. Explain the reaction with the help of chemical equation.

Question 37. Out of $Cu_2Cl_2$ and $CuCl_2$, which is more stable and why?

Question 38. When a brown compound of manganese (A) is treated with HCl it gives a gas (B). The gas taken in excess, reacts with $NH_3$ to give an explosive compound (C). Identify compounds A, B and C.

Question 39. Although fluorine is more electronegative than oxygen, but the ability of oxygen to stabilise higher oxidation states exceeds that of fluorine. Why?

Question 40. Although $Cr^{3+}$ and $Co^{2+}$ ions have same number of unpaired electrons but the magnetic moment of $Cr^{3+}$ is 3.87 B.M. and that of $Co^{2+}$ is 4.87 B.M. Why?

Question 41. Ionisation enthalpies of Ce, Pr and Nd are higher than Th, Pa and U. Why?

Question 42. Although Zr belongs to 4d and Hf belongs to 5d transition series but it is quite difficult to separate them. Why?

Question 43. Although +3 oxidation states is the characteristic oxidation state of lanthanoids but cerium shows +4 oxidation state also. Why?

Question 44. Explain why does colour of $KMnO_4$ disappear when oxalic acid is added to its solution in acidic medium.

Question 45. When orange solution containing $Cr_2O_7^{2–}$ ion is treated with an alkali, a yellow solution is formed and when $H^+$ ions are added to yellow solution, an orange solution is obtained. Explain why does this happen?

Question 46. A solution of $KMnO_4$ 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?

Question 47. The second and third rows of transition elements resemble each other much more than they resemble the first row. Explain why?

Question 48. $E^{\ominus}$ of Cu is + 0.34V while that of Zn is – 0.76V. Explain.

Question 49. The halides of transition elements become more covalent with increasing oxidation state of the metal. Why?

Question 50. 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?

Question 51. Reactivity of transition elements decreases almost regularly from Sc to Cu. Explain.

Question 52. Match the catalysts given in Column I with the processes given in Column II.

Question 53. Match the compounds/elements given in Column I with uses given in Column II.

Question 54. Match the properties given in Column I with the metals given in Column II.

Question 55. Match the statements given in Column I with the oxidation states given in Column II.

Question 56. Match the solutions given in Column I and the colours given in Column II.

Question 57. Match the property given in Column I with the element given in Column II.

Question 58. Match the properties given in Column I with the metals given in Column II.

Question 59. Assertion : $Cu^{2+}$ iodide is not known.

Reason : $Cu^{2+}$ oxidises $I^–$ to iodine.

Question 60. Assertion : Separation of Zr and Hf is difficult.

Reason : Because Zr and Hf lie in the same group of the periodic table.

Question 61. 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.

Question 62. Assertion : Cu cannot liberate hydrogen from acids.

Reason : Because it has positive electrode potential.

Question 63. Assertion : The highest oxidation state of osmium is +8.

Reason : Osmium is a 5d-block element.

Question 64. Identify A to E and also explain the reactions involved.

Question 65. 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.

Question 66. 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.

Question 67. On the basis of Lanthanoid contraction, explain the following :

(i) Nature of bonding in $La_2O_3$ and $Lu_2O_3$.

(ii) Trends in the stability of oxo salts of lanthanoids from La to Lu.

(iii) Stability of the complexes of lanthanoids.

(iv) Radii of 4d and 5d block elements.

(v) Trends in acidic character of lanthanoid oxides.

Question 68. (a) Answer the following questions :

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

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

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

(b) Identify the metal and justify your answer.

(i) Carbonyl M(CO)$_5$

(ii) $MO_3F$

Question 69. 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.

Question 70. (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.

Question 71. 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. $H_2SO_4$ and 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.