Which of the following formulae is used to calculate the depression in freezing point?

At $1 \ atm$ pressure,which of the following solutions will have the highest freezing point?

$A$ camphor sample melts at $176^{\circ} C$. $K_f$ for camphor is $40 \ K \ kg \ mol^{-1}$. $A$ solution of $0.02 \ g$ of a hydrocarbon in $0.8 \ g$ of camphor melts at $156.77^{\circ} C$. The hydrocarbon is made up of $92.3 \%$ of carbon. What is the molecular formula of the hydrocarbon?

Calculate the mass of ascorbic acid (Vitamin $C$,$C_{6}H_{8}O_{6}$) to be dissolved in $75 \ g$ of acetic acid to lower its melting point by $1.5 \ ^{\circ}C$. $K_{f} = 3.9 \ K \ kg \ mol^{-1}$.

If molality of the dilute solution is doubled,the value of molal depression constant $(K_f)$ will be

An aqueous solution of a weak monobasic acid containing $0.1 \text{ g}$ of the acid in $21.7 \text{ g}$ of water freezes at $272.813 \text{ K}$. If the value of $K_f$ for water is $1.86 \text{ K kg/mol}$, what is the molecular mass of the monobasic acid in $\text{g/mol}$? (Assume the freezing point of pure water is $273 \text{ K}$)