Which of the following form an ideal solution?

I. Chloroethane and bromoethane

II. Benzene and toluene

III. $$n$$-hexane and $$n$$-heptane

IV. Phenol and aniline

A solution containing 6.0 g of urea is isotonic with a solution containing 10 g of a non-electrolytic solute $$X$$. The molar mass of X (in g $$\mathrm{mol}^{-1}$$) is

$$x \%(w / V)$$ solution of urea is isotonic with $$4 \%$$ $$(w / V)$$ solution of a non-volatile solute of molar mass $$120 \mathrm{~g} \mathrm{~mol}^{-1}$$. The value of $$x$$ is

At $$T(\mathrm{~K}) \times \mathrm{g}$$ of a non-volatile solid (molar mass $$78 \mathrm{~g} \mathrm{~mol}^{-1}$$) when added to 0.5 kg water, lowered its freezing point by $$1.0^{\circ} \mathrm{C}$$. What is $$x$$ (in g)? ($$K_f$$ of water at $$T(\mathrm{~K})=1.86 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$$)