Abnormal Molecular Mass — Prelims Questions

Which of the following 0.1 M aqueous solutions will have the lowest freezing point?

A 0.01 M aqueous solution of K$_3$[Fe(CN)$_6$] has a freezing point of $-0.062^circ C$. If $K_f$ for water is $1.86^circ C,\text{kg/mol}$, what is the apparent degree of dissociation of K$_3$[Fe(CN)$_6$]?

Benzoic acid (C$_6$H$_5$COOH) forms a dimer in benzene. If the observed molecular mass of benzoic acid in benzene is $244,\text{g/mol}$, what is the degree of association ($\alpha$)? (Normal molecular mass of benzoic acid = $122,\text{g/mol}$)

A 0.5 M aqueous solution of a weak acid HA has an osmotic pressure of $12.3,\text{atm}$ at $27^circ C$. Calculate the percentage dissociation of the acid. (Given: $R = 0.0821,\text{L atm mol}^{-1}\text{K}^{-1}$)

Which of the following 0.05 M aqueous solutions will have the highest boiling point?

The osmotic pressure of a 0.01 M solution of an electrolyte is found to be $0.70,\text{atm}$ at $27^circ C$. Calculate the van't Hoff factor (i) for this electrolyte. (Given: $R = 0.0821,\text{L atm mol}^{-1}\text{K}^{-1}$)