Which 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)
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
A.
negligible Screening effect of 'f' orbitals
Lanthanoid contraction is the regular decrease in atomic and ionic radii of lanthanides. This is due to the imperfect shielding [or poor screening effect] of f-orbitals due to their diffused shape, which unable to counterbalance the effect of the increased nuclear charge. Hence, the net result is a contraction in size of lanthanoids.
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