Colligative Properties

The properties of the solutions which depend only on the number of solute particles, are called colligative properties, eg, relative lowering of vapour pressure, elevation in boiling point, depression in freezing point, osmotic pressure. While optical activity is not a colligative property.

will give the maximum number of particles ( , ions) in the solution. Hence, its elevation in boiling point is maximum and therefore, it has highest boiling point.

The mola depression constant for camphor is maximum. Hence, depression of freezing point will be maximum for camphor.

The boiling point of a liquid is the temperature at which its vapour pressure becomes equal to the atmospheric pressure. At high altitudes the atmospheric pressure becomes low, hence the boiling point of water decreases.

van't Hoff factor,


Since, sodium hydroxide is binary electrolyte,
degree of ionisation)

The dilute aqueous solution of sucrose cannot associated or dissociated. Hence, van't Hoff factor ' ' is one. (No association or dissociation) (For dissociation) (For association)

Step 1: Understand the Van't Hoff factor.
The Van't Hoff factor represents the number of particles into which a solute dissociates in solution.
For solutes that dissociate in water, such as salts, is greater than 1 because the solute dissociates into multiple ions.
Step 2: Identify the correct option.
For dissociating solutes (like NaCl), will be greater than 1, as each formula unit dissociates into two or more ions.

Step 1: Understanding Ideal Solutions
An ideal solution is one where the enthalpy of mixing is zero, and the intermolecular forces between the components are similar to those in the pure components.
In ideal solutions, the change in volume during mixing is also negligible.
Step 2: Analyzing the Given Options
Option (a) Benzene + Toluene and Option (b) n-Hexane + n-Heptane are examples of ideal solutions because their intermolecular forces are similar, and they form a solution with no significant heat or volume change.

Option (d) Ethyl bromide + Ethyl chloride is also an ideal solution because the intermolecular forces between these two substances are similar.
Step 3: Why Ethyl Alcohol + Water is Not Ideal
Ethyl alcohol and water do not form an ideal solution because their intermolecular forces are quite different.
Water forms hydrogen bonds, while ethanol also participates in hydrogen bonding but to a lesser extent.
This difference leads to an exothermic heat of mixing, making it a non-ideal solution.
Step 4: Conclusion Thus, ethyl alcohol and water are not an ideal solution.