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Question : 16
Total: 26
Give reasons :
(a)E ∘ value for Mn 3 + ∕ Mn 2 + couple is much more positive than that for Fe 3 + ∕ Fe 2 + .
(b) Iron has higher enthalpy of atomization than that of copper.
(c)Sc 3 + is colourless in aqueous solution whereas Ti 3 + is coloured.
(a)
(b) Iron has higher enthalpy of atomization than that of copper.
(c)
Solution:
(a) Because Mn 2 + is more stable than Mn 3 + due to half-filled d 5 configuration whereas Fe 2 + becomes unstable after loosing an electron from half filled orbital.
(b) Iron has higher enthalpy of atomization then that of copper because of higher number of unpaired electrons present in iron.Fe ( 3 d 6 4 s 2 ) possesses and unpaired electron while Cu ( 3 d 10 4 s 1 ) possesses only 1 unpaired electron.
Number of unpaired electronsα Inter atomic interaction α metallic bonding a entnalpy of atomization.
(c)Sc 3 + ( 3 d 0 ) is colourless in aqueous solution due to absence of unpaired electron and no d − d transition takes place. While Ti 3 + ( 3 d 1 ) is coloured due to the presence of one unpaired electron and d − d transition takes place which absorbs light in visible region.
(b) Iron has higher enthalpy of atomization then that of copper because of higher number of unpaired electrons present in iron.
Number of unpaired electrons
(c)
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