D-F Block Elements Transition Elements MCQs – 4

1) Transition metals usually exhibit highest oxidation states in their
a) Chlorides
b) Fluorides
c) Bromides
d) Iodides

2) The element with the electronic configuration 1s22s22p63s23p63d104s1 is
a) Fe
b) Co
c) Ni
d) Cu

3) Which of the following substances has the least ionic character ?

4) In the standardization of Na2S2O3 using K2Cr2O7 by iodometry, the equivalent weight of K2Cr2O7 is
a) (Molecular weight)/2
b) (Molecular weight)/6
c) (Molecular weight)/3
d) Same as molecular weight

5) Which are ferrous metals ?
a) Fe, Co, Ni
b) Ru, Rh, Pd
c) Os, Ir, Pt
d) Cr, Mn, Cu

6) TiCI4 fumes strongly in moist air and is hydrolysed to give
a) Ti

7) Which of the following is explosively unstable ?
d) MnO

8) Chloroplatinic acid is
a) Monobasic
b) Dibasic
c) Tribasic
d) Tetrabasic

9) Identify the wrong statement regarding copper sulphate
d) It gives CuO on strong heating in air

10) Monel metal is an alloy of
a) Cu + Zn + Ni
b) Cu + Ni + Fe
c) Cu + Sn + Pb
d) Cu + Ni + Al

11) Which is used as a fungicide ?
b) CuO and quick lime

12) Out of Fe2+, Fe3+,Mn2+ and Ti2+, the one with the smallest size is

13) The best antidote for HgCI2 is
a) The white of an egg
b) Oranges
c) Epsom salt
d) None of these

14) For the same transition metal ion, the colour of its compounds will depend upon the
a) Temperature of the reaction
b) Pressure of the reaction
c) Nature of ligands or Lewis bases attached to the metal ion
d) Concentration of the ligands

15) Transition elements are less reactive because of their
a) High ionisation energy
b) High heat of vapourisation
c) Lower heat of hydration of ions
d) All are correct

16) The magnetic moment of a transition metal ion is found to be 5.92 BM. The number of unpaired electrons present in it is
a) 2
b) 3
c) 4
d) 5

17) The equivalent weight of MnSO4 is equal to its molecular weight when it is converted to

18) @ The strength as oxidising agents of the following species in acidic solution decreases in the order
d) None of these

19) The sulphide which is not soluble in hot dilute HNO3 is
a) HgS
b) PbS
c) CuS
d) CdS

20) Which of the following forms stable dinuclear ions ?
a) Zn
b) Cd
c) Hg
d) Fe

21) Which among the following metals does not dissolve in aqua regia ?
a) Pt
b) Pd
c) Au
d) Ir

22) TiCI3 on heating gives
a) Ti

23) Hard steel contains
a) No carbon
b) 0.6-1.5% carbon
c) 5% carbon
d) 0.5-0.2% carbon

24) Tin (II) chloride is used
a) As a mordant in dyeing
b) As a reducing agent
c) In the preparation of colloidal gold
d) All the above

25) SnCI4 is
a) Tetrahedral in shape
b) A covalent compound
c) A volatile liquid
d) All the above

26) The basis for Al as a reducing agent in the thermite process is
b) High Eox. Pot. of Al
d) High I.E. of Al

27) Which of the following will not rapidly attack and destroy a pure aluminium can ?
a) NaOH solution
d) Conc. HCl

28) Which of the following properties of Al are not typical of most other metals ?
a) Considerable temperature difference between M.P. and B.P.
b) Negative standard electrode potential
c) Electrical resistance increases with increase in temperature
d) Forms salts with alkalies

29) Alum is

30) Common alum is

31) Alum is used by dyers of cloth
a) As first aid for cuts
b) For softening hard water
c) As mordant
d) For fire proofing fabrics

32) Aluminium metal is corroded in coastal places near to the sea, because the protective oxide film
a) Is removed by sea water
b) Reacts with sea water
c) Is attacked by salt present in sea water
d) Reacts with sand particles

33) Al(OH)3 is soluble in NaOH solution due to the formation of
a) Sodium aluminium hydroxide
b) Sodium meta aluminate
c) Aluminium peroxide
d) Aluminium oxide

34) Which of the following oxides is more stable than the others ?

35) A silvery white metal is solid on cold days but liquefies on a hot day and reacts with dilute HCI to give H2. It could be
a) Sn
b) Sb
c) Bi
d) Ga

36) Which of the following is amphoteric ?

37) Conc. HNO3 is stored in a container of
a) Cu
b) Al
c) Zn
d) Sn

38) Eka aluminium is
a) Gallium
b) Germanium
c) Indium
d) Scandium

39) Al and Ga have the same covalent radius because of the
a) Greater shielding power of the s-electrons of the Ga atom
b) Poor shielding power of the s-electrons of the Ga atom
c) Poor shielding power of the d-electrons of the Ga atom
d) Greater shielding power of the d-electrons of the Ga atom

40) Which of the following statements is false ?
a) Al compounds are ionic
b) Al is a light metal of great tensile strength
c) Al is a powerful reducing agent
d) Al does not react with steam even at high temperature

41) Which is correct in the case of anhydrous aluminium chloride ?
b) It is not easily hydrolysed
d) It is a strong Lewis base

42) Alumina
a) Is a good conductor of electricity
b) Is a bad conductor of electricity
d) Is an electrovalent compound

43) Next to diamond, the hardest substance is
a) AIN
c) BN

44) RRR If a person is injured by the shot of a gun and all the pellets could not be removed, it may cause poisoning by
a) Hg
b) Pb
c) Fe
d) As

45) The correct composition of Mohr salt is

46) Mohr salt on oxidation with conc. HNO3 gives
a) Potash alum
b) Chrome alum
c) Ferric alum
d) None of these

47) In the volumetric analysis, Mohr salt is preferred to ferrous sulphate because
c) it can undergo both oxidation and reduction

48) Mohr salt is prepared from an equimolar solution of
a) Green vitriol and potassium sulphate
b) Green vitriol and ammonium sulphate
c) Blue vitriol and potassium sulphate
d) Blue vitriol and ammonium sulphate

49) The formula of malachite is

50) The formula of azurite is

51) Malachite and azurite are used respectively as
a) Blue and green pigments
b) Green and blue pigments
c) Red and green pigments
d) Green and red pigments

52) Lunar caustic is
a) NaOH
b) KOH

53) Silver nitrate is also called
a) Silver glance
b) Horn silver
c) Lunar caustic
d) Ruby silver

54) When AgNO3 comes in contact with skin, it leaves a black stain. This is because of
c) Its reduction to silver
d) Its oxidation to silver oxide

55) AgNO3 solution is kept in coloured bottles in the laboratory. This is done
a) Because colours in glass act as negative catalysts
b) To cut off the entry of light
c) Simply to give it a distinction from other reagent bottles as it is costly

56) The soluble complex formed on adding NH4OH to AgNO3 solution is

57) Which of the following chemicals is used as an eye drop in trachoma?

58) The chemist who has helped in the discovery of the maximum number of transuranic elements in the last two decades is
a) Sir Robert Robinson
b) Sir J.J. Thomson
c) Prof. G.T. Seaberg
d) Sir C.N. Hinshelwood

59) Which of the following metal oxides is white in colour but becomes yellow on heating?
b) ZnO
c) FeO
d) MgO

60) Lanthanide contraction implies a
a) Decrease in density
b) Decrease in mass
c) Decrease in ionic radii
d) Decrease in radioactivity

61) Which of the following pairs of elements has identical atomic size?
a) Ti, Zr
b) Zr, Hf
c) Na, K
d) La, Hf

62) Lutetium (Lu) is
a) A transition element
b) A lanthanide
c) An actinide
d) A p-block element

63) The element which is present in every amalgam is
a) Copper
b) Silver
c) Iron
d) Mercury

64) The atomic radii of the transition elements in a row are
a) Smaller than those of the s-block as well as p-block elements
b) Greater than those of the s-block as well as p-block elements
c) Smaller than those of the s-block but greater than those of the p-block
d) Greater than those of the s-block but smaller than those of the p-block.

65) The magnetic moment of a transition metal ion is found to be 3 . 87 B. M. The number of unpaired electrons present in it is
a) 2
b) 3
c) 4
d) 5

66) Which of the following are d-block elements but not regarded as transition elements?
a) Cu, Ag, Au
b) Zn, Cd, Hg
c) Fe, Co, Ni
d) Ru, Rh, Pd

67) Which of the following transition metals has the highest melting point?
a) Cr
b) Mo
c) W
d) Hg

68) The element showing the most stable +8 oxidation state in its compounds is
a) Ru
b) Mn
c) Re
d) Os

69) Which of the following does not contain a covalent bond?

70) Which of the following does not show colour due to charge transfer spectra?

71) Which of the following statements is incorrect?
c) Mercurous ion is colourless

72) The correct order of reactivity of halogens with the 3d- transition series is
a) F < Cl < Br < I
b) F > Cl > Br > I
c) Cl > Br > I > F
d) I > Br > Cl > F

73) The ionic character of the halides of metals (3 d-transi-tion series) decreases in the order
a) M – l > M – Br > M – Cl > M – F
b) m – Cl > M – Br > M – l > M – F
c) M – Br > M – Cl > M – F > M – l
d) M – F > M – Cl > M – Br > M – l

74) Which of the following sulphides is not black in colour?
a) CuS
b) MnS
c) CoS
d) NiS

75) Chromite ore has the formula
d) Both (a) and (b)

76) In alkaline medium, the equivalent mass of KMnO4 is(M = molecular mass)
d) M

77) If M is an element of the actinide series, the degree of complex formation decreases in the order

78) The lanthanides used in glass blowers goggles are
a) Pr and Nd
b) Eu and Gd
c) Tb and Dy
d) Pm and Sm

79) Low spin complexes are generally formed by elements of the
a) 3d-Series
b) 4d-Series
c) 5d-Series
d) Both (b) and (c)

80) If the lanthanide element with xf electrons has a pink colour, then the lanthanide with (14 – x) f
electrons will have the colour

a) Blue
b) Red
c) Green
d) Pink

81) Which lanthanide compound is used in a most powerful liquid laser after dissolving it in selenium oxychloride?
a) Cerium oxide
b) Neodymium oxide
c) Promethium sulphate
d) Ceric sulphate

82) K2Cr2O7 is preferred to Na2Cr2O7 for use in volumetric analysis as a primary standard because
d) None of the above

83) Which of the following transition metals shows variable valency?
a) Sc
b) Y
c) Fe
d) Ac

84) The first man made (synthetic) transition metal is
a) Pm
b) Tc
c) Nb
d) Zr

85) Which of the following groups of transition metals is called coinage metals?
a) Cu, Ag, Au
b) Ru, Rh, Pd
c) Fe, Co, Ni
d) Os, Ir, Pt

86) The metal used for making armoured steel for tanks and domestic safes is
a) Mn
b) Al
c) Pb
d) Cr

87) Pt dissolves in aqua regia due to the formation of

88) The most abundant transition metal is
a) Zn
b) Fe
c) Hg
d) Au

89) The transition metal used for making joints in jewellery is
a) Zn
b) Cu
c) Ag
d) Cd

90) Browns catalyst is
a) Pt/PtO
c) Nickel boride
d) None

91) CuSO4 solution + lime is called
c) Fehling solution
d) Bordeaux mixture

92) A mixture of TiO2 and BaSO4 is called
a) Titanox
b) Lithopone
c) White pigment
d) None

93) The most common oxidation state of the lanthanide series is
a) +2
b) +3
c) +4
d) +1

94) Vanadyl ion is

95) Which of the following cannot reduce acidified solution of MnO4 ion ?
c) H (nascent)

96) In aqueous solution, Eu2+ ion acts as
a) An oxidising agent
b) A reducing agent
c) Either (a) or (b)
d) None of these

97) Cerium can show the oxidation state of + 4 because
a) It resembles the carbon family
b) It has a very low value of I.E.
c) Of its tendency to attain the noble gas configuration of Xenon
d) Two s and two f electrons can be lost easily

98) Which of the following contains the maximum number of unpaired electrons ?

99) Which of the following is paramagnetic ?

100) The deep blue colour produced on adding H2O2 to acidified K2Cr2O7 solution is due to the formation of


Ans 1) b

Ans Desc 1) F being highly electronegative, stabilises the highest oxidation states of transition metals

Ans 2) d

Ans Desc 2) Cu (Z = 29) = 3d10 4s1 outer electronic configuration

Ans 3) b

Ans Desc 3) Zn, Cd, Hg have a pseudo noble gas configuration (n – 1) d10 ns2 which exerts a strong polarising power on the anions, which decreases from Zn2+ to Hg2 + as the size increases in that order. Thus ZnCI2 due to the greater polarising power of Zn2 + is the most covalent and least ionic in character

Ans 4) b

Ans Desc 4) In iodometry, Kl reacts with K2Cr2O7 in acidic medium to give I2 which is titrated against Na2S2O3.
K2Cr2O7 +7 H2SO4 +6 Kl 4 K2SO4+ Cr2(SO4)3 +7H2O +3I2
(6×127 parts)
2 Na2S203 + I2 Na2S406 +2NaI
2×27 parts
For 1M Na2S203 , 127 parts of iodine is required which is obtained from – M of K2Cr2O7 Hence equivalent weight of K2Cr2O7 = (Molecular weight)/6

Ans 5) a

Ans Desc 5) Fe, Co and Ni are called ferrous metals

Ans 6) d

Ans Desc 6) TiCI4 + 4 H2O Ti(OH)4 + 4 HCI

Ans 7) a

Ans Desc 7) Mn2O7 is highly unstable and decomposes on warming to give MnO2
2 Mn2O7 4 MnO2 + 3 O2

Ans 8) b

Ans Desc 8) Chloroplatinic acid is H2[RCI6] which is dibasic

Ans 9) b

Ans Desc 9) Cu2+ cannot oxidise CI ions to CI2 as Cl is a weaker reducing agent than l

Ans 10) a

Ans Desc 10) Monel metal is an alloy of Cu, Ni and Fe which is used for construction of electrolytic vessels and is used in the preparation of fluorine by the Moissan method

Ans 11) a

Ans Desc 11) CuSO4 + Ca(OH)2 mixture is called Bordeaux mixtureand is used as a fungicide

Ans 12) d

Ans Desc 12) Size increases in the order Fe3+ < Fe2+ < Mn2 + < Ti2+ as the nuclear charge decreases

Ans 13) a

Ans Desc 13) The white of an egg, which provides an alternative protein material

Ans 14) c

Ans Desc 14) The colour of the compounds of the same transition metal ion depends upon the nature of ligands attached to it. For example, [CuCI4]2- is greenish yellow, [Cu(H2O)4]2+ is blue but [Cu(NH3)4]2+ + is violet or deep blue

Ans 15) d

Ans Desc 15)

Ans 16) d

Ans Desc 16) Applying meff = Ön (n + 2), meff = 5.92
B.M.is obtained from n = 5

Ans 17) a

Ans Desc 17) In MnSO4, the oxidation state of Mn = + 2. In Mn2O3, the oxidation state of Mn = + 3. There is an increase of oxidation state by 1 when MnSO4 changes to Mn2O3. Hence its equivalent mass is equal to its molecular mass.

Ans 18) c

Ans Desc 18) E° values (standard reduction potentials) for these species in acidic medium are
S2O2-8 (aq) + 2 e 2 SO24 (aq) ;
E° = +2.01 Volts
MnO4 (aq)+8 H +5 e Mn2+ (aq)+4 H2O ;
E° =+ 1.77 volts
Cr2O2– (aq) + 14 H+ + 6 e 2 Cr3+ + 7 H2O ;
E° = +1.33 volts
Thus strength as oxidising aont decreases in the order S2O2– > MnO4 > Cr2O2-7

Ans 19) a

Ans Desc 19) HgS is not soluble in hot dil.HNO3. It dissolves only in aqua regia

Ans 20) a

Ans Desc 20) Hg in the mercurous state forms (Hg – Hg)2+ or the Hg22+ stable dinuclear ion which is diamagnetic

Ans 21) d

Ans Desc 21) Ir does not dissolve in aqua regia as it is much more noble than Au or Pt

Ans 22) d

Ans Desc 22) 2TiCI3 TiCI2 + TiCI4. It is a disproportionate reaction

Ans 23) b

Ans Desc 23) Hard steel contains 0.6-1.5% C

Ans 24) d

Ans Desc 24) Tin (II) chloride, SnCI2 is a reducing agent. Therefore, it can form colloidal gold from gold salt solutions.

Ans 25) d

Ans Desc 25) All the statements mentioned are correct.

Ans 26) c

Ans Desc 26) In the thermite process, the reaction is highly exothermic. Much heat is produced which is sufficient to melt the metal. The metal oxide is reduced by aluminium.

Cr2O3 + 2Al Al2O3 + 2Cr + Heat.

Ans 27) c

Ans Desc 27) Because aluminium becomes passive in conc. HNO3 , due to the formation of an oxide film.

Ans 28) d

Ans Desc 28) Al reacts with strong alkalies to form meta aluminates and aluminates.

2Al + 2NaOH + 2H2O 2NaAlO2 + 3H2

2Al + 6NaOH 2Na3AlO3 + 3H2

Ans 29) d

Ans Desc 29) Alum(Na2SO4.Al2(SO4)3.24H2O) are true double salts, soluble in water and ionise giving simple ions in solution.

Ans 30) a

Ans Desc 30) Common alum is K2SO4.Al2(SO4)3.24H2O.

Ans 31) c

Ans Desc 31) Alum is used as a mordant in dyeing.

Ans 32) c

Ans Desc 32)

Ans 33) b

Ans Desc 33) 2Al + 2NaOH + 2H2O 2NaAlO2 + 3H2.

Ans 34) b

Ans Desc 34) Tl2O is most stable among these.

Ans 35) d

Ans Desc 35) The m.p. of Ga is only 30oC. It gives hydrogen when reacts with dilute HCl.

2Ga + 6HCl 2GaCl3 + 3H2.

Ans 36) c

Ans Desc 36)

Ans 37) b

Ans Desc 37) Aluminium becomes passive in conc. HNO3 due to the formation of an oxide film.

Ans 38) a

Ans Desc 38) Eka aluminium is now called gallium.

Ans 39) c

Ans Desc 39) Because of the poor shielding power of the d-electrons in the Ga atom.

Ans 40) a

Ans Desc 40) Al forms ionic and covalent compounds both.

Ans 41) c

Ans Desc 41) Anhy. AlCl3 sublimes at 1000C under vacuum.

Ans 42) b

Ans Desc 42) Alumina is a bad conductor of electricity.

Ans 43) d

Ans Desc 43) B4C is next hardest to diamond.

Ans 44) b

Ans Desc 44) Bullets contains lead. So lead poisoning may occur.

Ans 45) d

Ans Desc 45)

Ans 46) c

Ans Desc 46) FeSO4 of Mohr’s salt is oxidised to Fe2(SO4)3 by HNO3 in presence of an acid.The new compound is known as ferric alum.
2 HNO3 2 NO2 + H2O+O
FeSO4 + H2SO4 + O Fe2(SO4)3 + H2O
Thus the compound
(N4)2SO4 .Fe2(SO4)3 .24 H2O is known as ferric alum

Ans 47) b

Ans Desc 47) Mohrs salt is less easily oxidizable than FeSO4 and gives a more stable solution

Ans 48) b

Ans Desc 48)

Ans 49) a

Ans Desc 49) Malachite is CuCO3 .Cu(OH)2 which is green in colour

Ans 50) b

Ans Desc 50) Azurite is 2 CuCO3 .Cu(OH)2 which is deep blue in colour

Ans 51) b

Ans Desc 51)

Ans 52) d

Ans Desc 52)

Ans 53) c

Ans Desc 53)

Ans 54) c

Ans Desc 54) In contact with organic matter (skin, cloth etc) AgNO3 is reduced to metallic silver (which has a black colour) 2AgNO3 + H2O2Ag + 2 HNO3 + O

Ans 55) b

Ans Desc 55) To cut off the entry of light, AgNO3 solution is kept in coloured bottles

Ans 56) b

Ans Desc 56) AgNO3 + 3 NH4OH[Ag (NH3)2]OH + NH4NO3 + H2O

Ans 57) a

Ans Desc 57)

Ans 58) c

Ans Desc 58) Prof. G.T. Seaberg has contributed the most in the discovery of the maximum number of transuranic elements

Ans 59) b

Ans Desc 59) ZnO on heating develops a metal excess defect due to interstitial cations and electrons. It loses oxygen reversibly.The colour is due to the excitation of interstitial electrons.

Ans 60) c

Ans Desc 60) Lanthanide contraction implies decrease in ionic radii

Ans 61) b

Ans Desc 61) Due to lanthanide contraction, Zr and Hf have identical atomic sizes

Ans 62) b

Ans Desc 62) Lutetium (Lu) is the last member of the lanthanide series

Ans 63) d

Ans Desc 63) An alloy is known as an amalgam when one of the constituent metals is mercury

Ans 64) c

Ans Desc 64) The atomic radii of transition elements in a row are smaller than those of the s-block but greater than those of the p-block elements

Ans 65) b

Ans Desc 65) Magnetic moment, eff = 3.87 B.M. corresponds to the number of unpaired electrons, n = 3 by applying the formula
eff = B.M.
For n = 1 = 1.73 B.M. for n = 2, = 2.83 B.M. for n = 3, = 3.87 B.M.and so on

Ans 66) b

Ans Desc 66) Zn, Cd, Hg are d-block elements but not regarded as transition elements, so these do not have partly filled d-orbitals in their most common oxidation states

Ans 67) c

Ans Desc 67) Tungsten, W has the highest melting point (3683 K) among the d-block elements

Ans 68) d

Ans Desc 68) Both W and Os show +8 oxidation state in their compounds but the +8 oxidation state shown by Os is more stable as compared to that of Ru

Ans 69) a

Ans Desc 69) CoCI2 is an ionic compound whereas other compounds have metal-oxygen covalent bonds

Ans 70) c

Ans Desc 70) [Cu(H2O)4]2+ shows a blue colour due to d – d transition

Ans 71) a

Ans Desc 71) Mercurous ion exists as Hg22+ where there exists a covalent bond between two Hg+ ions as [Hg – Hg]2+

Ans 72) b

Ans Desc 72) The reactivity order of halogens with transition metals is F > Cl > Br > I; F being the most reactive halogen

Ans 73) d

Ans Desc 73) F being highly electronegative and smaller in size forms an F ion which is not polarised by the metal cation and thus forms an ionic bond

Ans 74) b

Ans Desc 74) MnS is light pink (flesh) coloured whereas other sulphides are black in colour

Ans 75) d

Ans Desc 75) Chromite ore is FeCr2O4 or FeO .Cr2O3

Ans 76) a

Ans Desc 76) In alkaline medium the reaction of KMnO4 is
2 KMnO4 + H2O 2 MnO2 + KOH+3 O
or +2H2O+3e MnO2+40H
Therefore, equivalent mass of KmnO4=

Ans 77) c

Ans Desc 77) The higher the charge on the metal ion, the smaller is the ionic size and the more is the complex forming ability. Thus, the degree of complex formation decreases in the order > MO22+ > > MO2+
The higher tendency of complex formation of MO22+ as compared to M3 + is due tothe high concentration of charge on the metal atom M in MO22+

Ans 78) a

Ans Desc 78) Pr and Nd ions added to glass absorb yellow sodium light and find their use in glass blowers goggles as light filters

Ans 79) d

Ans Desc 79) As the crystal field splitting in the case of complexes of metal ions in the 4d and 5d-transition series are much larger, the electrons of the metal ion are paired up first in the lower energy set of orbitals before going to the higher energy set within the same d-subshell causing maximum pairing and thus low spin (or spin paired) complexes are formed

Ans 80) d

Ans Desc 80) In case of lanthanides, the element with xf electrons has a similar colour to that of (14 – x) f electrons

Ans 81) b

Ans Desc 81) Neodymium oxide, (Nd2O3) dissolved in selenium oxychloride is one of the most powerful liquid lasers known so far

Ans 82) a

Ans Desc 82) Na2Cr2O7 is hygroscopic and cannot be used as a primary standard in volumetric analysis

Ans 83) c

Ans Desc 83) Fe shows variable valency as +2 and +3 whereas Sc, Y and Ac show only +3 valency

Ans 84) b

Ans Desc 84)

Ans 85) a

Ans Desc 85) Cu, Ag, Au group of elements are called coinage metals as these are used in minting coins

Ans 86) a

Ans Desc 86) Manganese steel containing 1.2-15% Mn is used for making rock crushing machinery,armour plates, safes etc

Ans 87) d

Ans Desc 87) Pt + 2 HNO3 + 8 HCI H2PtCI6 + 2 NOCI + 4 H2O

Ans 88) b

Ans Desc 88) Fe is the most abundant and most widely used transition element

Ans 89) d

Ans Desc 89)

Ans 90) c

Ans Desc 90)

Ans 91) d

Ans Desc 91)

Ans 92) a

Ans Desc 92)

Ans 93) b

Ans Desc 93)

Ans 94) a

Ans Desc 94) Vanadyl ion is VO2 + where V is in the +4 oxidation state

Ans 95) b

Ans Desc 95)

Ans 96) b

Ans Desc 96) Eu2+ has a strong tendency to be oxidised to more stable Eu3+.Therefore, it acts as a reductant

Ans 97) c

Ans Desc 97) By losing all the electrons of 4f, 5d and 6s orbitals Ce4+ acquires the more stable noble gas configuration of Xe

Ans 98) b

Ans Desc 98) Mn2+ in MnCI2 has the maximum number (five) of unpaired electrons

Ans 99) a

Ans Desc 99) In carbonyl complexes, the metal atoms are in the zero oxidation state and the CO ligand is very strong which can cause forcible pairing of the 4s electrons within the 3d level. The ground state electronic configuration of the V atom = 3d3 4s2 = 3d1 d1 d1 d° d° 4s2 4px° py° pz° The excited state electronic configuration of the V atom = 3d2 d2 d1 d° d° 4s° 4px° py° pz° In V(CO)6, V undergoes d2sp3– hybridization leaving one unpaired electron in the unhybridized d-orbital due to which it is paramagnetic

Ans 100) c

Ans Desc 100) Cr2O72- +4H2O2 + 2 H+ 2 CrO5 + 5 H2O
Chromic peroxide, deep blue colour

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