Given below are two statements: one is labeled as Assertion (A) and the other is labeled as Reason (R): Assertion (A): Helium is used to dilute oxygen in the diving apparatus. Reason (R): Helium has a high solubility in $O_2$. In light of the above statements, choose the correct answer from the options given below:

Isotonic solutions have the same:

A solution containing $10 \text{ g/dm}^3$ of urea (molecular mass $= 60 \text{ g mol}^{-1}$) is isotonic with a $5 \%$ solution of a non-volatile solute. The molecular mass of this non-volatile solute is:

Which colligative property provides the most accurate method for determining the molecular weight of proteins and polymers?

The vapour pressure of a solvent decreased by 10 mm of Hg when a non-volatile solute was added to the solvent. The mole fraction of the solute in solution is 0.2. What would be the mole fraction of the solvent if the decrease in vapour pressure is 20 mm of Hg?

Which one is not equal to zero for an ideal solution?

The freezing point depression constant ($K_f$) of benzene is $5.12 \text{ K kg mol}^{-1}$. The freezing point depression for the solution of molality $0.078 \text{ m}$ containing a non-electrolyte solute in benzene is:

The molarity of a $0.2 \text{ N } Na_2CO_3$ solution will be:

Of the following $0.10 \text{ m}$ aqueous solutions, which one will exhibit the largest freezing point depression?