Question

Isotonic solutions must have the same
A.Solute
B.Density
C.Elevation in boiling point
D.Depression in freezing point

Answer 1

Hint:First we must know what an isotonic solution is. Isotonic solution means two solutions which have the same osmotic pressure across a semipermeable membrane. It also has the same osmolarity as another solution. This state provides free movement of water across the membrane without changing the concentration of solutes on both the sides. The question can have multiple correct options.

Complete step-by-step answer:As we know isotonic solutions have the same osmotic pressure and also the same concentration. Elevation in boiling point and depression in freezing point are both colligative properties. A colligative property is said to be a property of a solution which is dependent on the ratio between the total number of solute particles in the solution to the total number of the solvent particles. Colligative properties are not dependent on the chemical nature of the solution’s components.
As mentioned above, the molar concentration is the same for isotonic solutions, so elevation in boiling point and depression in freezing point of isotonic solutions must be the same.
Hence the correct option is C and D which says elevation in boiling point and depression in freezing point will be the same for isotonic solutions.

Note:Colligative properties can be linked to several quantities which expresses the concentration of a solution, such as molarity, normality, and molality. The four colligative properties that are exhibited by a solution are: boiling point elevation, freezing point depression, relative lowering of vapour pressure and osmotic pressure. Few examples of isotonic solutions are $0.9\% $ normal saline and lactated ringers.