Calculate the solubility (in $\text{moles/litre}$) of a saturated aqueous solution of $Ag_3PO_4$ if the vapour pressure of the solution becomes $750 \ torr$ at $373 \ K$. (Assume vapour pressure of pure water at $373 \ K$ is $760 \ torr$ and density of water is $1 \ g/mL$)

Identify the false statement:

$A$ substance '$X$' $(1.5 \ g)$ dissolved in $150 \ g$ of a solvent '$Y$' (molar mass $= 300 \ g \ mol^{-1}$) led to an elevation of the boiling point by $0.5 \ K$. The relative lowering in the vapour pressure of the solvent '$Y$' is . . . . . . $\times 10^{-2}$. (Nearest integer)
[Given : $K_{b}$ of the solvent $= 5.0 \ K \ kg \ mol^{-1}$]
Assume the solution to be dilute and no association or dissociation of $X$ takes place in solution.

Which one of the following statements is false?

At $T \ K$,the vapour pressure of pure benzene $(C_6H_6)$ and toluene $(C_7H_8)$ are $75 \ mm \ Hg$ and $22 \ mm \ Hg$ respectively. $23.4 \ g$ of benzene and $64.4 \ g$ of toluene are mixed to form an ideal solution. If the vapours are in equilibrium with the liquid mixture,the mole fraction of toluene in the vapour phase is (Atomic weight: $C=12, H=1$).

An aqueous solution of urea (molar mass $= 60 \ g \ mol^{-1}$) boils at $100.18^o C$ at atmospheric pressure. If $K_f = 1.86 \ K \ kg \ mol^{-1}$ and $K_b = 0.512 \ K \ kg \ mol^{-1}$ for water,then the freezing point of the solution is equal to ..... $^o C$.