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InterviewSolution
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What is lanthanide contraction ? Explain the cause of lanthanide contraction. Draw the structures of chloroxylenol and adenine. How are ethylamine and ethyl methyl amine distinguished by using nitrous acid ? |
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Answer» Solution :LANTHANOID contraction may be defined as gradual decrease in atomic and ionic radii of lanthanoids with the increase in atomic number. Cause of lanthanoid contraction : As the atomic number of the members of lanthanoids sries increases the positive charge on nucleus increases by '+ 1' unit and one more electron ENTERS in the same 4f subshell. There is imperfect shielding of one electron by another electron in the same '4f' subshell. The extent of shielding for electrons is less in '4f' subshell as COMPARED to electrons in d subshell. 4f shells have diffused shapes. Hence, with increase of nuclear charge the valence shell is pulled slightly towards nucleus. As a RESULT of the pull the size of `M^(3+)` ions goes on decreasing. Structure of chloroxylenol :  Ethylamine forms ethyl alcohol with nitrous acid whereas ethyl methyl amine gives N-nitrosoethyl-methyl amine nitrous acid. (a) `underset("Ethyl amine")(C_(2)H_(5)-NH_(2))+underset("Nitrous acid")(HO-N=O)overset(NaNO_(2)+HCl)rarr underset("Ethyl alcohol")(C_(2)H_(5)-OH+N_(2)uarr) + H_(2)O` (b) `underset(" Ethyl methyl amine")(C_(2)H_(5)-underset(CH_(3))underset("|")("N ")-H)+HO-N=O overset(NaNO_(2)+HCl)rarr underset("N-nitroso ethyl-methyl amine")(C_(2)H_(5)-underset(CH_(3))underset("|")("N ")-N=O+H_(2)O)` |
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