Page 1 : FINAL REVISION & PRACTICE CHEMISTRY XII CBSE 2022, UNIT: 4: THE d- AND f-BLOCK ELEMENTS, What are transition elements? Write two characteristics of the transition elements., Calculate the number of unpaired electrons in the following gaseous ions: Mn3+,Cr3+, V3+and Fe2+. Which one of these, is the most stable in aqueous solution., 3. How would you account for the following :, a) Zn, Cd and Hg are not considered as transition elements. Why, b) Scandium is a transition element but Zinc is not., c) Copper atom has completely filled d orbital (3d10) in its ground state, yet it is transition element., d) Silver atom has completely filled d orbital (4d10) in its ground state, yet it is transition element., 1., 2., , 4., , 5., , 6., 7., 8., , 9., , 10., 11., , 12., , Explain giving a suitable reason for each of the following, a) Transition elements exhibit higher enthalpies of, g) Zinc is soft whereas Cr is hard., atomization., h) Chromium is a typical hard metal while mercury, b) In the series Sc(Z = 21) to Zn (Z = 30), the, is a liquid., enthalpy of atomisation of zinc is the lowest, i) There occurs much more frequent metal –metal, c) Transition metals have high melting and boiling, bonding in compounds of heavy transition, points., elements(3rd series)., d) Fe has higher melting point than Cu., j) Metal –metal bonding is more frequent for the, e) Chromium group elements have highest melting, 4d & 5d series of transition metals than that for, points., the 3d series., f) Transition elements are much harder than alkali, metals., Assign reasons for the following :, a) Transition element form generally coloured, d) Cu+ salts are colourless while Cu2+ salts are, compounds., Coloured, b) Sc+3 is colourless, while Ti3+ is Coloured, e) The Transition metals ions such as Cu+ Ag+, c) Zn+2 salts are white ,but Cu+2 are blue., Sc+3 are colourless., 3+ 3+, +, Predict which of the following will be colored in aqueous solution? Ti ,V ,Cu ,Sc3+, Mn2+, Fe3+& Co2+., Out of Ag2SO4,CuF2,MgF2 and CuCl which compound will be coloured and why?, Explain the following observations., a) Transition metals show paramagnetic behavior., b) Mn2+ exhibits maximum paramagnetism, (a) Explain Variation in magnetic behaviour of Transition Metals along 3d transition series., (b) Calculate the magnetic moment of a divalent ion in aqueous solution if its at.no is 25., (c) Calculate the ‘spin only’ magnetic moment of M2+ion (Z = 27), Explain Variation in Atomic Size of Transition Metals along 3d transition series., Account for the following :, a) Members of second (4d) and the third (5d) series in each group of transition elements have similar radii., b) Zr and Hf exhibit similar properties., c) Although Zr belongs to 4d and Hf belongs to 5d transition series but it is quite difficult to separate them., d) Radius of Fe+2 is less than Mn+2., Assign reasons for the following, a) There is in general increase in density of, d) Transition metals form interstitial, element from titanium to copper, compounds., b) Transition metal ions form complexs, e) Most of transition metals form alloys., c) Most of the transition metals and their, compounds possess catalytic properties., , 13. Explain briefly how +2 state becomes more and more stable in the first half of the first row transition elements with, , increasing atomic number?, 14. Explain the following observations., a) Transition element show variable oxidation state., b) Mn Shows the highest oxidation state of +7 among 3d series elements., c) The greatest number of oxidation states are exhibited by the elements in the middle of transition series., d) Mn Shows the highest oxidation state of +7 with oxygen but with fluorine it shows the highest oxidation state of +4., e) Highest fluoride of Mn is MnF4 whereas the highest oxide is Mn2O7., f) Mn2+compounds more stable than Fe2+towards oxidation to their +3 state., 15. Account for the following :, , a), b), c), d), , Of the 3d4species, Cr2+is strongly reducing while Mn3 is strongly oxidising., Cr2+ is a stronger reducing agent Fe2+., The lowest oxide of transition metal is basic, the highest is amphoteric/acidic., Mno is basic while Mn2O7 is acidic in nature., , MAHENDRA KALRA, , Page 1 of 2

Page 2 : e) CrO42- is a strong oxidizing agent while MnO4-2 is not, f) The increasing oxidising power of oxoanions are in the VO2+<Cr2O72-<MnO416. Explain the following observations:, a) The Eo(M2+/M) values are not regular for the first row transition metals., b) E0value for the Mn3+/Mn2+couple much more positive than that forCr3+/Cr2+or Fe3+/Fe2+, c) E0value for the Mn2+/Mn much more than expected., d) E0value for the Cu2+/Cu is positive ., 17. Assign reasons for the following, a. Transition metal exhibit higher oxidation state in oxides and fluorides., b. Highest fluoride of Mn is MnF4 wheras the highest oxide is Mn2O7, c. The highest oxidation state is exhibited in oxoanions of a metal., 18. Account for the following, a) Irregular variation of ionization, d) First Ionization enthalpy of Cr is lower, enthalpies (first and second) in the first, than that of Zinc., series of the transition elements., e) Mn+3undergoes disproportionation, b) +3 state of Mn is of little importance., reaction easily., c) The Third ionization enthalpy of, f) d1 configuration is very unstable in ions., manganese is exceptionally high,, 19. Account for the following :, a) Cu+ ion is not stable in aqueous solutions., b) Cu+ ion has d10 configuration while Cu+2 has d9configuration,still Cu+2 is stable in aqueous solutions, c) Cobalt (II) is stable in aqueous solution but in the presence of complexing reagents it is easily oxidized., d) Cobalt (II) is easily oxidized in the presence of strong ligands., e) Although Co2+ ion appears to be stable ,it is easily oxidized to Co3+ ion in the presence of a strong ligand., f) Unlike Cr3+,Mn+2,Fe+3 and the subsequent other M2+ ions of the 3d series of elements ,the 4d and the 5d series, metals generally do not form stable cationic species., g) Transistion elements tend to be unreactive with increasing atomic number in the series., ANSWER THE FOLLOWING:1., 2., 3., 4., 5., 6., 7., 8., , Name a transition element which does not exhibit variable oxidation states, Which of the 3d transition series metals exhibits the largest number of oxidation states and why, 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, 3d8and 3d4?, Which metal in the first series of transition metals exhibits +1 oxidation state most frequently and why?, 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., What may be the possible oxidation states of transition metals with the following electronic configuration in the ground, states in their atoms?(i)3d34s2(ii)3d54s2(iii)3d64s2, Which is a stronger reducing agent Cr2+or Fe2+and why?, Among Elements of 3d transition series : Write the element (a) which is not regarded as transition element. (b)which can, show an oxidation state of +1. (c) Which element is soft (d) which shows maximum number of oxidation states. (e) Which, element has the highest melting point (f) Which element shows only +3 state?, (g) Which element is a strong oxidizing agent in + 3 oxidation state and why. (h) Which element is a strong reducing agent, in + 2 oxidation state and why., , Topic: LANTHANOIDS 1. Give Reasons for the following, (a), (b), (c), (d), (e), (f), (g), (h), (i), (j), 1., 2., 3., , Chemistry of all the lanthanoids are quite similar., Size of trivalent lanthanoid cations decreases with increase in the atomic number, It is difficult to separate lanthanoid elements in pure state.., Ce4+ in aqueous solution is a good oxidising agent., Ce4+ is used oxidising agent in volumetric analysis., Ce3+ can be easily oxidized to Ce4+., d-block elements exhibit more oxidation states than f block elements., Eu2+ is a strong reducing agent., La3+ and Lu3+do not show any colour in solutions., Although Zr belongs to 4d and Hf belongs to 5d transition series but it is quite difficult to separate them., What is Lanthanoid contraction? Give its cause. What are its Consequences?, Name an important alloy which contains some of the lanthanoid metals. Mention its uses., Explain the chemistry of lanthanoids with reference to (i)electronic configuration (ii)Oxidation state (iii) atomic size and, ionic size (iv)chemical reactivity, 4. Name the members of the lanthanoid series which exhibit +4 oxidation states and those which exhibit +2 oxidation states., 5. Use Hund’s rule to derive the electronic configuration of Ce 3+ion, and calculate its magnetic moment on the basis of ‘spinonly’ formula., , MAHENDRA KALRA, , Page 2 of 2