During the determination of the molar mass of benzoic acid in benzene using the freezing point depression method,it corresponds to which of the following?

The depression in freezing point observed for a formic acid solution of concentration $0.5 \, mL \, L^{-1}$ is $0.0405^{\circ} \, C$. The density of formic acid is $1.05 \, g \, mL^{-1}$. The Van't Hoff factor of the formic acid solution is nearly: (Given for water $K_{f} = 1.86 \, K \, kg \, mol^{-1}$)

When $1.5 \ g$ of phenol $(C_6H_5OH)$ is dissolved in $100 \ g$ of toluene,a decrease in freezing point of $0.56 \ K$ is observed. If the association is dimeric in nature,find the percentage of association. Given: $K_f = 4 \ K \ kg \ mol^{-1}$.

$0.004 \ M \ Na_2SO_4$ is isotonic with $0.01 \ M$ glucose. The degree of dissociation of $Na_2SO_4$ is ........... $\%$.

$2\,g$ of benzoic acid $(C_6H_5COOH)$ dissolved in $25\,g$ of benzene shows a depression in freezing point equal to $1.62\,K$. The molal depression constant $(K_f)$ for benzene is $4.9\,K\,kg\,mol^{-1}$. What is the percentage degree of association of the acid?

For a $0.1 \ M$ $Ba(NO_3)_2$ solution,the van't Hoff factor is $2.74$. The degree of dissociation is ....... $\%$.