Question

Isotonic solutions must have the same _____________.

• A. elevation in boiling points
• B. density
• C. depression in freezing points
• D. solute

Answer 1

Answer: (A), (C)

depression in freezing points

Isotonic solutions

Two solutions having the same osmotic pressure across a semipermeable membrane are referred to as isotonic solutions.

Due to the same osmotic pressure, the concentration of the isotonic solutions will remain the same at a given temperature.

$\pi =CRT$

Where,

$\pi =\text{Osmotic pressure}$

$C=\text{Concentration of solution}$

$T=\text{Absolute temperature}$

Relation between isotonic solutions and colligative properties

Elevation in boiling point and depression in freezing point are colligative properties, which depends upon concentration.

As the molar concentration is the same for isotonic solutions, elevation in boiling point and depression in freezing point of isotonic solutions must be the same.

Hence, options (C) and (D) are the correct answers.