Question

The colligative properties of a solution depend on
A.The number of solute particles present in it
B.The chemical nature of the solute particles present in it
C.The nature of the solvent used
D.None

Answer 1

We can define colligative properties as properties of a solution that depend only on the concentration of solute particles. They consist of changes in the vapor pressure, boiling point, and freezing point of the solvent in the solution.

Complete step by step answer:
The colligative properties includes,
Vapor pressure depression of the solvent
Elevation of the boiling point
Depression in the freezing point
Osmotic pressure
Vapor pressure depression of the solvent: The equilibrium between a liquid and its vapor produces a characteristic vapor pressure for each substance that depends on the temperature. The lowering of the vapor pressure is caused by a lesser ability of the solvent to evaporate, so equilibrium is reached with a smaller concentration of the solvent in the gas phase. The vapor pressure of a solution is expressed using Raoult’s law:
${P_{solv}} = {\chi _{solv}}{P^o}_{solv}$
The vapor pressure of the solvent $\left( {{P_{solv}}} \right)$ above a dilute solution is equal to the mole fraction of the solvent $({\chi _{solv}})$ times the vapor pressure of the pure solvent $\left( {{P^o}_{solv}} \right)$. The difference between the vapor pressure of the pure solvent and the vapor pressure of the solution$(\Delta P)$is proportional to the concentration of the solute and is given by the equation,
$\Delta P = {\chi _{solute}}{P^o}_{solv}$
The vapor pressure depression of the solvent is a colligative property, because it is proportional to the concentration of the solute. Raoult’s law is applicable to dilute solutions. The unit of the concentration of the solute in vapor pressure is expressed in mole fraction.
Boiling-point elevation: The effect of the solute concentration on the boiling point is given by the equation,
$\Delta {T_b} = m{k_b}$
Here,
$\Delta {T_b} =$Increase in the boiling point (difference in boiling point of solution and boiling point of the solvent).
$m =$Molal concentration of the solute
${k_b} =$Boiling point elevation constant (depends on the type of solvent used).
The concentration unit in boiling point elevation is expressed in terms of molality.
Freezing point depression: The freezing point depression is proportional to the concentration of the solute particles and is given by the equation,
$\Delta {T_f} = m{k_f}$
Here,
$\Delta {T_f} =$Freezing point of the solution
$m =$Molal concentration of the solute
${k_f} =$Freezing point depression constant (depends on the solvent used).
The concentration unit in freezing point depression is expressed in terms of molality.
Osmotic pressure: The osmotic pressure of solution is defined as the difference in pressure needed for no net transfer of solvent to occur across a semipermeable membrane that separates the solution from the pure solvent. The osmotic pressure of a solution is proportional to the molar concentration of the solute particles in the solution and the equation is given by,
$\Pi = MRT$
Here, $\Pi =$Osmotic pressure
$M =$Molar concentration of the solute
$R =$Ideal gas constant
$T =$Temperature (in Kelvin)
The concentration in osmotic pressure is expressed in terms of molarity.
Colligative properties depend on the number of solute particles in the solution.
“i” is the number of particles. We can say the solute would dissociate on mixing with the solvent as the number of particles. With the help of the molality of a solution and the number of particles a compound will dissolve to form, it is possible to predict the solution with the lowest freezing point.
Therefore, the option (A) is correct.
Colligative properties of solutions are properties that depend on the concentration of solute molecules or ions, and not on the identity of the solute.
The nature of the solvent matters as the solution properties are the same to the pure solvent. But the nature of the solute does not since we are considering the solutes are all similar to the given solvent such as dissolves like.
Therefore, option (C) is also correct.

Note:
We know that the colligative properties are those properties of solutions, which depend on the ratio of the number of solute particles to the number of solvent molecules in a solution, and not on the nature of the chemical species present. The number ratio can be related to the various units for concentration of a solution such as molarity, molality, normality etc. Properties of solution are independent of nature of solute particles are exact for ideal solutions, and are approximate for dilute real solutions. In other words, colligative properties are a set of solution properties that could be reasonably approximated by assuming that the solution is ideal.