Which of the following aqueous molal solutions has the highest freezing point?

Which of the following solutions exhibits the highest freezing point depression?

$C_{6}H_{6}$ freezes at $5.5^{\circ} C$. The temperature at which a solution of $10 \ g$ of $C_{4}H_{10}$ in $200 \ g$ of $C_{6}H_{6}$ freezes is $...... \ ^{\circ} C$. (The molal freezing point depression constant of $C_{6}H_{6}$ is $5.12 \ ^{\circ} C/m$.)

What is the molality of a solution that has a freezing point depression of $3 \ K$ and a freezing point depression constant of $5 \ K \ kg \ mol^{-1}$ (in $m$)?

$2 \ g$ of a non-electrolyte solute (molar mass is $500 \ g \ mol^{-1}$) was dissolved in $57.3 \ g$ of xylene. If the freezing point depression constant $K_f$ of xylene is $4.3 \ K \ kg \ mol^{-1}$,then the depression in freezing point of xylene is.......... (in $K$)

Two elements $A$ and $B$ form compounds with molecular formulas $AB_2$ and $AB_4$. When $1 \ g$ of $AB_2$ is dissolved in $20 \ g$ of $C_6H_6$,the freezing point decreases by $2.3 \ K$. When $1 \ g$ of $AB_4$ is dissolved in $20 \ g$ of $C_6H_6$,the freezing point decreases by $1.3 \ K$. The molal depression constant for benzene is $5.1 \ K \ kg \ mol^{-1}$. Calculate the atomic weights of $A$ and $B$.