The molecular weights of sodium chloride and glucose are determined by the depression of freezing point method. As compared to their theoretical molecular weights, what will be their observed molecular weights when determined by the above method ? Justify your answer.

Explanation

The depression of freezing point is used to determine the molecular weight of solutes.
`m=(K_(f)xxw xx 1000xx i)/(DeltaT_(f)xx W)`
The molecular weight calculated is found to be slightly different from the theoretical value as the solute added to the solution acts as an electrolyte. It further undergoes either association or dissociation resulting in either increase or decrease in their molecular weights. KCl being an electrolyte undergoes dissociation, releasing into two ions [K+ and Cl- for which iis greater than 1. Although in KCl, experimental molecular weight is found to be greater than observed value. Whereas, for glucose, its experimental value is found to be smaller than observed value as it is non-electrolyte for which value of iis 1