Grade 12Inorganic Chemistry
Why do colligative properties yield abnormal molar mass in case of certain electrolytes
Why do colligative properties yield abnormal molar mass in case of certain electrolytes
1 Answer
Arun
The compounds which dissociate or associate in the solvent show abnormal molecular masses.
(i) Association: Compounds like benzoic acid or ethanoic acid dimerise in benzene due to hydrogen bonding as a result of which the number of particles in the solution decreases. Since colligative properties depend upon number of particles, such solutes show lower colligative property.
(ii) Dissociation: Electrolytes like NaCl, KCl, etc. dissociate into ions which result in increased number of particles, hence higher value of colligative property.
To account for association or dissociation van’t Hoff introduced a factor i known as van’t Hoff factor.
(i) Association: Compounds like benzoic acid or ethanoic acid dimerise in benzene due to hydrogen bonding as a result of which the number of particles in the solution decreases. Since colligative properties depend upon number of particles, such solutes show lower colligative property.
(ii) Dissociation: Electrolytes like NaCl, KCl, etc. dissociate into ions which result in increased number of particles, hence higher value of colligative property.
To account for association or dissociation van’t Hoff introduced a factor i known as van’t Hoff factor.