Multiple Choice QuestionsWhich one of the following statements is correct when SO2 is passed through acidified K2Cr2O7 solution?
The solution is decolourized
SO2 is reduced
Green Cr2(SO4)3 is formed
The solution turns blue
Because of lanthanoid contraction, of elements which of the following elements have nearly same atomic radii ? (Number in the parenthesis are atomic number).
Ti (22) and Zr(40)
Zr(40) and Nb (41)
Zr (40) and Hf (72)
Zr (40) and Hf (72)
C.
Zr (40) and Hf (72)
Because of the lanthanoid contraction Zr (atomic radii 160 pm) and Hf (atomic radii 158 pm) have nearly same atomic radii.
Lanthanoids include the elements from lanthanum La (Z=57) to lutetium Lu(Z =71).Zirconium Zr (40) belong to the second transition series (4d) and Hf (72) belongs to third transition series (5d). Lanthanoid contraction is associated with the intervention of the 4f orbitals which are filled before the 5d- series of elements starts. The filling of 4f if orbitals before 5d orbitals result in a regular decrease in atomic radii which compensates the expected increases in atomic size with increasing atomic number. As a result of this lanthanoid contraction, the elements of second and third transition series have almost similar atomic radii.
In acidic medium,H2O2 changes Cr2O72- to CrO5 which has two (-O-O-) bonds. Oxidation state of Cr in CrO3 is
+5
+3
+6
+6
Reason of lanthanoid contraction is
negligible Screening effect of 'f' orbitals
increasing the nuclear charge
decreasing the nuclear charge
decreasing the nuclear charge
Which of the following does not give oxygen on heating?
KClO3
Zn(ClO3)2
K2Cr2O7
K2Cr2O7
Which of the following lanthanoid ions is diamagnetic?
(At. number; Ce =58, Sm =62, Eu =63, Yb = 70)
Ce2+
Sm2+
Eu2+
Eu2+
KMnO4 can be prepared from K2MnO4 as per reaction
The reaction can go to completion by removing OH- ions by adding
HCl
KOH
CO2
CO2
Which one of the following does not correctly represent the correct order of the property indicated aginst it?
Ti < V<Cr< Mn: increasing number of oxidation states
Ti< V<Cr3+<Mn3+ : increasing magnetic moment
Ti < V < Cr < Mn : Increasing melting points
Ti < V < Cr < Mn : Increasing melting points
Four successive members of the first series of the transition metals are listed below. For which one of them, the standard potential value
has a positive sign?
Co (Z=27)
Ni (Z=28)
Cu (Z=29)
Cu (Z=29)
The catalytic activity of transition metals and their compounds is ascribed mainly to
their magnetic behaviour
their unfilled d- orbitals
their ability to adopt variable oxidation states
their ability to adopt variable oxidation states
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