Which of the following statements concerning the properties of solutions describes a colligative effect?

When $0.1 \, m$ $CH_3COOH$ is present in a solvent,it shows an elevation in boiling point of $0.75 \, ^oC$. The acid dissociation constant $(K_a)$ will be: (Given: $K_b = 5 \, K \, kg \, mol^{-1}$)

In which solution,solute is liquid and solvent is gas?

$100 \ g$ each of two solutions,one containing $20 \%$ by mass of $NaOH$ and the other $40 \%$ by mass of $NaOH$,are mixed. The density of the resulting solution is $1.25 \ g/mL$. Find the new $\% \ w/v$ of $NaOH$ in the final solution.

Consider the following aqueous solutions.
$I$. $2.2 \ g$ Glucose in $125 \ mL$ of solution.
$II$. $1.9 \ g$ Calcium chloride in $250 \ mL$ of solution.
$III$. $9.0 \ g$ Urea in $500 \ mL$ of solution.
$IV$. $20.5 \ g$ Aluminium sulphate in $750 \ mL$ of solution.
The correct increasing order of boiling point of these solutions will be:
[Given: Molar mass in $g \ mol^{-1}$: $H=1, C=12, N=14, O=16, Cl=35.5, Ca=40, Al=27, S=32$]

$A$ solution has a $1:4$ mole ratio of pentane to hexane. The vapour pressure of the pure hydrocarbons at $20 \ ^oC$ are $440 \ mm \ Hg$ for pentane and $120 \ mm \ Hg$ for hexane. The mole fraction of pentane in the vapour phase would be