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Colligative Properties
In chemistry, colligative properties are properties that depend on the relative concentration of solute particles in a solution, but not on the nature of the solute particles. In other words, colligative properties are properties that depend on the number of solute particles, not on their chemical nature. The most important colligative property is vapor pressure lowering.
Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid or solid phase. The higher the vapor pressure of a liquid or solid, the more easily it will vaporize. Vapor pressure is directly proportional to the temperature of the liquid or solid.
When a solute is dissolved in a liquid, the vapor pressure of the liquid decreases. This is because the addition of the solute particles to the liquid decreases the number of vapor molecules in contact with the liquid surface. This decrease in vapor pressure is called vapor pressure lowering.
The vapor pressure lowering of a solution is directly proportional to the number of solute particles in the solution. For example, if you dissolve twice as much sugar in a glass of water, the vapor pressure of the water will be lowered by twice as much.
The vapor pressure lowering of a solution can be used to calculate the boiling point of the solution. The boiling point is the temperature at which the vapor pressure of the liquid equals the atmospheric pressure. When you dissolve a solute in a liquid, the boiling point of the liquid increases. This increase in boiling
Colligative Properties of a Solution Include
The colligative properties of a solution are its freezing point, boiling point, osmotic pressure, and vapor pressure. These properties are all affected by the number of solute particles in the solution. The more solute particles in a solution, the higher its freezing point, boiling point, osmotic pressure, and vapor pressure.
Relative Lowering of Vapour Pressure
The vapour pressure of a liquid is lowered when it is mixed with another liquid. The reason for this is that the vapour pressure of a liquid is a measure of the tendency of the molecules of the liquid to escape into the surrounding air. When two liquids are mixed, the molecules of each liquid will come into contact with the molecules of the other liquid. This will result in the formation of molecules that are a combination of the two liquids. These molecules will have a lower vapour pressure than the molecules of either of the two liquids that formed them.
Mathematically Raoult’s Law can be Expressed in the Form:
P = ρRT
Where,
- P is the Vapor Pressure
- ρ is the Density of the Vapor
- R is the Universal Gas Constant
- T is the Temperature
Derivation of Raoult’s Law
The derivation of Raoult’s law is as follows:
The vapor pressure of a pure liquid is given by the Clausius-Clapeyron equation as
where
- P is the vapor pressure of the liquid
- R is the universal gas constant
- T is the temperature
- ΔH is the enthalpy of vaporization
- From the ideal gas law,
where
- n is the number of moles of gas
- V is the volume of the gas
- P is the pressure of the gas
- R is the universal gas constant
- T is the temperature
Ideal Solutions and Deviations From Raoult’s Law
- The vapor pressure of a pure liquid is always greater than the vapor pressure of the same liquid when it is mixed with an ideal gas.
- The vapor pressure of a mixture is always less than the vapor pressure of the pure liquids.
- The vapor pressure of a mixture is always greater than the vapor pressure of the ideal gas.
Determination of Molecular Mass From Vapour Pressure Lowering
The molecular mass of a compound can be determined from the vapour pressure lowering of the compound. The higher the molecular mass of a compound, the more it will weigh and the higher the vapour pressure. The lower the vapour pressure, the more condensed the molecules are and the higher the molecular mass.
Measurement of Lowering of Vapour Pressure
The vapour pressure of a liquid can be lowered by adding a solid that has a higher vapour pressure. The solid will sublime, or change from a solid to a gas, and the vapour pressure of the liquid will be lowered as a result.
The apparatus used to measure the lowering of vapour pressure is shown in the diagram below.
The liquid is placed in the beaker and the solid is placed on the wire gauze. The wire gauze is then heated with the Bunsen burner. The vapour pressure of the liquid will be lowered as the solid sublime.
The apparatus can be used to measure the vapour pressure of a liquid before and after the addition of a solid. The difference in the two readings will be the result of the lowering of the vapour pressure.
Ostwald and Walker’s Dynamic Method (Gas Saturation Method):
This equation is used to calculate gas saturation in porous media.
formula_1
Where:
formula_2 is the gas saturation
formula_3 is the porosity
formula_4 is the gas permeability
formula_5 is the gas viscosity
formula_6 is the gas density
The Ostwald and Walker dynamic method is a more general version of the Kozeny-Carman equation. It accounts for the effects of gas viscosity and density on gas saturation.
What are Colligative Properties?
Colligative properties are the properties of a solution that are not due to the chemical nature of the solute, but to the number of solute particles present.
Colligative Properties Examples
Solution Properties
A solution is a homogeneous mixture of two or more substances. The properties of a solution depend on the nature of the substances dissolved in it and on the relative amounts of each substance.
The following are some general properties of solutions:
1. Solutions are generally more soluble than the substances that make them up.
2. Solutions are more dense than the substances that make them up.
3. Solutions are more viscous than the substances that make them up.
4. Solutions are more volatile than the substances that make them up.
5. Solutions are more stable than the substances that make them up.
6. Solutions are more acidic than the substances that make them up.
7. Solutions are more alkaline than the substances that make them up.
Various Types of Colligative Properties of Solution
The following are the types of colligative properties of solution:
1. Boiling Point Elevation
2. Freezing Point Depression
3. Vapor Pressure Depression
4. Osmotic Pressure
1. Bringing Down of Vapor Pressure
The vapor pressure of a liquid is the pressure exerted by the vapor of the liquid in equilibrium with the liquid at a given temperature. The higher the vapor pressure of a liquid, the greater the tendency of the liquid to evaporate.
A high vapor pressure is usually associated with a low boiling point. For example, the vapor pressure of water at room temperature is much higher than the vapor pressure of mercury. This is why water boils at a lower temperature than mercury.
One way to reduce the vapor pressure of a liquid is to lower its temperature. This is why liquids with high vapor pressures are often stored in refrigerators. Another way to reduce the vapor pressure is to increase the surface area of the liquid. This is why liquids are often stored in bottles with small openings.
2. Height in Boiling Point
The boiling point of a liquid is the temperature at which the vapor pressure of the liquid is equal to the atmospheric pressure.
The higher the boiling point of a liquid, the greater the vapor pressure of the liquid.
3. Vapor Pressure
The vapor pressure of a liquid is the pressure of the vapor of the liquid in equilibrium with the liquid.
The higher the vapor pressure of a liquid, the greater the tendency of the liquid to vaporize.
3. Sadness in Freezing Point
The manga features a lot of sadness, but the saddest scene in my opinion is when Tohru visits Kyo’s house and finds out that he has been frozen. It is heartbreaking to see her cry and mourn for him.
4. Osmotic Pressure
The osmotic pressure of a solution is the pressure that is necessary to prevent the diffusion of solvent molecules into a solution of solute molecules. The osmotic pressure of a solution is determined by the number of solute molecules in the solution and the size of the solute molecules. The osmotic pressure of a solution increases as the number of solute molecules in the solution increases and as the size of the solute molecules increases.
