Define Colligative Properties. Explain all four colligative properties with their respective formulas and show how they are used to determine the molar mass of non-volatile solutes.

Q: Define Colligative Properties. Explain all four colligative properties with their respective formulas and show how they are used to determine the molar mass of non-volatile solutes.

Definition of Colligative Properties\nProperties of solutions that depend only upon the number of solute particles (molecules or ions) dissolved in a definite amount of the solvent, and not upon their chemical nature or identity, are called colligative properties. The term 'colligative' is derived from the Latin word colligare, meaning 'bound together'. The Four Colligative Properties Relative Lowering of Vapour Pressure: According to Raoult's law, the relative lowering of vapour pressure of a solution containing a non-volatile solute is equal to the mole fraction of the solute in the solution. $$\frac{P1^0 - P1}{P1^0} = x2 = \frac{n2}{n1 + n2}$| For dilute solutions ($n2 \ll n1$): $$\frac{P1^0 - P1}{P1^0} = \frac{w2 \cdot M1}{M2 \cdot w1}$$ Molar mass ($M2$) can be calculated easily using this relation. Elevation of Boiling Point ($\Delta Tb$): The boiling point of a liquid is the temperature at which its vapour pressure equals atmospheric pressure. Addition of a non-volatile solute lowers the vapour pressure, elevating the boiling point. $$\Delta Tb = Kb \cdot m = Kb \cdot \frac{w2 \times 1000}{M2 \times w1}$$ Where $Kb$ is the ebullioscopic constant. Depression of Freezing Point ($\Delta Tf$): The freezing point is the temperature at which the vapour pressure of the liquid equals the vapour pressure of the solid. Addition of a solute lowers the freezing point. $$\Delta Tf = Kf \cdot m = Kf \cdot \frac{w2 \times 1000}{M2 \times w1}$$ Where $Kf$ is the cryoscopic constant. Osmotic Pressure ($\pi$): Osmotic pressure is the extra pressure applied to the solution side to prevent osmosis through a semipermeable membrane. $$\pi = C \cdot R \cdot T = \frac{w2}{M2} \cdot \frac{R \cdot T}{V}$$ Osmotic pressure is preferred over other colligative properties for determining large molar masses of polymers and proteins because measurements are done at room temperature and the effect is large even at low concentrations.

Question

Accepted Answer

Definition of Colligative Properties
Properties of solutions that depend only upon the number of solute particles (molecules or ions) dissolved in a definite amount of the solvent, and not upon their chemical nature or identity, are called colligative properties. The term 'colligative' is derived from the Latin word colligare, meaning 'bound together'. The Four Colligative Properties Relative Lowering of Vapour Pressure: According to Raoult's law, the relative lowering of vapour pressure of a solution containing a non-volatile solute is equal to the mole fraction of the solute in the solution. $$\frac{P1^0 - P1}{P1^0} = x2 = \frac{n2}{n1 + n2}$| For dilute solutions ($n2 \ll n1$): $$\frac{P1^0 - P1}{P1^0} = \frac{w2 \cdot M1}{M2 \cdot w1}$$ Molar mass ($M2$) can be calculated easily using this relation. Elevation of Boiling Point ($\Delta Tb$): The boiling point of a liquid is the temperature at which its vapour pressure equals atmospheric pressure. Addition of a non-volatile solute lowers the vapour pressure, elevating the boiling point. $$\Delta Tb = Kb \cdot m = Kb \cdot \frac{w2 	imes 1000}{M2 	imes w1}$$ Where $Kb$ is the ebullioscopic constant. Depression of Freezing Point ($\Delta Tf$): The freezing point is the temperature at which the vapour pressure of the liquid equals the vapour pressure of the solid. Addition of a solute lowers the freezing point. $$\Delta Tf = Kf \cdot m = Kf \cdot \frac{w2 	imes 1000}{M2 	imes w1}$$ Where $Kf$ is the cryoscopic constant. Osmotic Pressure ($\pi$): Osmotic pressure is the extra pressure applied to the solution side to prevent osmosis through a semipermeable membrane. $$\pi = C \cdot R \cdot T = \frac{w2}{M2} \cdot \frac{R \cdot T}{V}$$ Osmotic pressure is preferred over other colligative properties for determining large molar masses of polymers and proteins because measurements are done at room temperature and the effect is large even at low concentrations.

MP Board · Class 12 · Chemistry · SolutionsDefine Colligative Properties. Explain all four colligative properties with their respective formulas and show how they are used to determine the molar mass of non-volatile solutes.

The Four Colligative Properties