Which of the following is/are "not correct" for $\mathrm{CH}_3 \mathrm{OH}+\mathrm{CH}_3 \mathrm{COOH}$ mixture solution?

1. 1. $\Delta H_{\text {mix }}<0$

2. 2. Does not obey Raoult's law.

3. 3. $\Delta H_{\text {mix }}>0$

4. 4. An example of ideal solution.

Henry's law is valid for

(A) ammonia gas dissolution in water

(B) $\mathrm{O}_2$ gas dissolution in unsaturated blood

(C) $\mathrm{O}_2$ dissolution in water

(D) $\mathrm{CO}_2$ dissolution in water

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