$150 \ g$ of acetic acid was contaminated with $10.2 \ g$ ascorbic acid $(C_{6}H_{8}O_{6})$ to lower its freezing point by $(x \times 10^{-1})^{\circ} C$. The value of $x$ is (Nearest integer). [Given $K_{f} = 3.9 \ K \ kg \ mol^{-1}$; Molar mass of ascorbic acid $= 176 \ g \ mol^{-1}$]

$x$ moles of $CO(NH_2)_2$ are present in $1200 \ g$ of water. If the freezing point of the solution is $-4.02 \ ^oC$,calculate the value of $x$. Given $k_f \ (H_2O) = 1.86 \ K \ kg \ mol^{-1}$.

Identify $(i)$,$(ii)$ and $(iii)$ in the following diagram representing the depression in freezing point:

The addition of $0.643 \,g$ of a compound to $50 \,mL$ of benzene (density $= 0.879 \,g \,mL^{-1}$) lowers the freezing point from $5.51^{\circ}C$ to $5.03^{\circ}C$. If the freezing point constant,$K_f$ for benzene is $5.12 \,K \,kg \,mol^{-1}$,the molar mass of the compound is approximately $..... \,g \,mol^{-1}$.

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 $B$.

$C_{6}H_{6}$ 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 $5.12 \ ^{\circ} C/m$.)