If a solute associates in a solvent, its experimentally calculated molar mass using the boiling point elevation method will be

$20 \ g$ of naphthoic acid $(C_{11}H_8O_2)$ $(M_w = 172 \ g/mol)$ is dissolved in $50 \ g$ of benzene. The freezing point depression of $2 \ K$ is observed for the solution. The Van't Hoff factor $(i)$ will be ($K_f$ for benzene $= 1.72 \ K \ kg \ mol^{-1}$)

The observed osmotic pressure of a solution of benzoic acid in benzene is less than its expected value because:

$A$ non-volatile solute '$A$' tetramerizes in water to the extent of $80\%$. $2.5 \text{ g}$ of '$A$' in $100 \text{ g}$ of water lowers the freezing point by $0.3^\circ \text{C}$. The molar mass of $A$ in $\text{g mol}^{-1}$ is ($K_f$ for water $= 1.86 \text{ K kg mol}^{-1}$)

$2 \ g$ 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 for benzene is $4.9 \ K \ kg \ mol^{-1}$. The percentage of benzoic acid in dimeric form is ......... $\%$.

The observed molar mass determined for $Na_2SO_4$ by the freezing point depression method is $50.0 \ g/mol$. The theoretical molar mass of $Na_2SO_4$ is $142 \ g/mol$. What will be the degree of dissociation $\alpha$ for $Na_2SO_4$ in water?