Which of the following are correct for an ideal solution?

(A) $\Delta V_{\text {mix }}=0$

(B) $V_{\text {solvent }}+V_{\text {solute }}=V_{\text {solution }}$

(C) $\Delta H_{\text {mix }}=0$

(D) $\mathrm{H}_2 \mathrm{O}+\mathrm{CO}_2 \longrightarrow \mathrm{H}_2 \mathrm{CO}_3$ is an example of ideal solution

At $0^{\circ} \mathrm{C}$ urea solution has an osmotic pressure of 400 mm . On dilution by $x$ times, its osmotic pressure decreased to 100 mm at $20^{\circ} \mathrm{C}$. The dilution factor $x$ is approximately

Relative lowering of vapour pressure of a dilute solution is 0.5 . What is the mole fraction of the non-volatile solute?

The solubility product of a sparingly soluble $A B_2$ salt is $2.56 \times 10^{-4} \mathrm{M}^3$ at $25^{\circ} \mathrm{C}$. The $K_f$ of water is 1.8 K kg mol ${ }^{-1}$. The depression in freezing point of a standard solution of $A B_2$ is