Kohlrausch's Law of Independent Migration of Ions:
Statement:
Kohlrausch's law of independent migration of ions states that the molar conductivity of an electrolyte at infinite dilution is the sum of the contributions of the individual ions present in the electrolyte. In other words, the conductivity of a solution at infinite dilution is determined by the conductivity of each ion in the solution when it is not affected by the presence of other ions.
Mathematical Form:
The molar conductivity (\(\Lambda_m^\infty\)) at infinite dilution for a strong electrolyte can be expressed as:
\(\Lambda_m^\infty = \lambda_+^\infty + \lambda_-^\infty\)
where: - \(\Lambda_m^\infty\) is the molar conductivity at infinite dilution of the electrolyte. - \(\lambda_+^\infty\) is the limiting molar conductivity of the cation. - \(\lambda_-^\infty\) is the limiting molar conductivity of the anion.
Implication:
According to this law, the contributions of the cation and anion to the total conductivity are independent of each other. This is particularly useful in calculating the conductivity of electrolytes at infinite dilution and in understanding the behavior of ions in a solution.
Write IUPAC names of the following compounds and classify them into primary, secondary and tertiary amines.
(i) (CH3 )2CHNH2 (ii) CH3 (CH2 )2NH2 (iii) CH3NHCH(CH3 )2
(iv) (CH3 )3CNH2 (v) C6H5NHCH3 (vi) (CH3CH2 )2NCH3 (vii) m–BrC6H4NH2
Give one chemical test to distinguish between the following pairs of compounds.
(i) Methylamine and dimethylamine
(ii) Secondary and tertiary amines
(iii) Ethylamine and aniline
(iv) Aniline and benzylamine
(v) Aniline and N-methylaniline
Account for the following:
(i) pKb of aniline is more than that of methylamine.
(ii) Ethylamine is soluble in water whereas aniline is not.
(iii) Methylamine in water reacts with ferric chloride to precipitate hydrated ferric oxide.
(iv) Although amino group is o– and p– directing in aromatic electrophilic substitution reactions, aniline on nitration gives a substantial amount of m-nitroaniline.
(v) Aniline does not undergo Friedel-Crafts reaction.
(vi) Diazonium salts of aromatic amines are more stable than those of aliphatic amines. (vii) Gabriel phthalimide synthesis is preferred for synthesising primary amines.