BITSAT 2016 Paper

(a) V=3d34s2;V2+=3d3=3 unpaired electrons
Cr=3d54s1;Cr2+=3d4=4 unpaired electrons
Mn=3d54s2 ;
Mn2+=3d5=5 unpaired electrons
Fe=3d64s2;Fe2+=3d6=4 unpaired electrons
Hence the correct order of paramagnetic behaviour
V2+<Cr2+=Fe2+<Mn2+
(b) For the same oxidation state, the ionic radii generally decreases as the atomic number increases in a particular transition series. hence the order is
Mn++>Fe++>Co++>Ni++
(c) In solution, the stability of the compound depends upon electrode potentials, SEP of the transitions metal ions are given as
Cr3+/Cr2+=−0.41,Sc3+
is highly stable as it does not show +2 O. S.
(d) Sc−(+2),(+3)
Ti−(+2),(+3)(+4)
i.e. Sc<Ti<Cr=Mn