Partial vs Vapor Pressure: Difference and Comparison

Pressure is used to apply some force in order to move something forward. It is used in both physics and chemistry as well. There are different types of pressures, and each has its own definition, advantages, disadvantages, and unique features.

Both Partial Pressure and Vapor Pressure are used in science and are common in all the curriculums across the countries. 

Key Takeaways

  1. Partial pressure measures individual gas component pressure within a mixture, while vapor pressure measures the pressure exerted by a liquid’s vapor in equilibrium with its condensed phase.
  2. The concept of partial pressure is based on Dalton’s Law of partial pressures, whereas vapor pressure is related to the boiling point of a liquid and varies with temperature.
  3. Partial pressure applies to gas and liquid mixtures, while vapor pressure is specific to liquids in equilibrium with their vapor phase.

Partial Pressure vs Vapor Pressure

Partial pressure refers to the pressure exerted by one gas in a mixture of gases. Vapour pressure refers to the pressure exerted by the vapour of a liquid in equilibrium with its own liquid state. Partial pressure is a property of a gas mixture, while vapour pressure is a property of a liquid.

Partial Pressure vs Vapor Pressure
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Partial pressure is used to deal with pressure and gases. We can even find partial pressure for all the elements in chemistry. Sometimes we can’t really call it partial pressure.

It depends upon the type of molar ratios of the gas container we use. The formula for Partial Pressure is P = P1+P2+P3. The pressure will increase depending on the problem we deal with.

We can simply explain the concept of vapour pressure by boiling water. It will be very helpful to understand the concept in a fast and easier manner.

When we boil the water at higher altitudes, the vapour pressure used to be low there so that the water boils faster and reaches 100 degrees faster. The formula for Vapor Pressure is P solution = X solvent * P solvent.

Comparison Table

Parameters of ComparisonPartial PressureVapor Pressure
Formula P = P1+P2+P3  P solution = X solvent * P solvent
LawDalton’s LawRaoult’s Law
PhaseSolid and LiquidGas
CalculationMole Fraction of the SoluteMole Fraction of the Gas
DependencyIndependentDependent

What is Partial Pressure?

In simple words, we can define partial pressure as a container filled with many gases. Each gas is used to exert pressure. The container which contains any one of the gas-filled insides is called partial pressure.

It has a separate law called Dalton’s Law of Partial Pressure. It is used in both chemistry and physics topics. It comes under the category of different types of pressures.

It is mainly used to measure the thermodynamic activity of the molecules of the gas. The symbol used for partial pressure is P or p. The symbol p is used as a subscript to identify pressure. Its features are also used in biology.

It is very important as it helps us to predict the movement of gas molecules. Because gases are used to pressure in two ends and the regions connected.

The partial pressure in liquid can be defined as when the gas would be in an equilibrium position in contact with the liquid. We can increase the partial pressure by simply decreasing its volume. The reactants contain two moles of gases so that the pressure of the reactant will be squared. 

partial pressure

What is Vapor Pressure?

When we place a liquid in a vessel, it will get heated, and the molecules will be seen and move in different directions at high speed. The reason for this is the kinetic energy possessed in that liquid.

On the other hand, the molecules of the liquid will rise and it will occupy the surfaces of the liquid. This process is simply called Evaporation. The molecules that pop up on the surface of the liquid are called Vapors.

Vapour Pressure can sometimes be called Vapor Equilibrium Pressure. There are many characteristics of vapour pressure. Temperature acts as the main aspect that affects vapour pressure.

When we raise the temperature, the vapour pressure will also rise. The evaporation process will depend on two following factors as Nature of the liquid and the Effect of Temperature. It contains Raoult’s Law of Expression. 

When we have the highest boiling point, we will be able to attain the lowest vapour pressure. It is related to evaporation. It is again used in both chemistry and physics.

Diethyl Ether is the highest vapour pressure in Chemistry. Molecules containing the strongest intermolecular forces are considered the lowest vapour pressure in Chemistry.

vapor pressure

Main Differences Between Partial Pressure and Vapor Pressure

  1. Partial Pressure uses Dalton’s law to explain, while Vapor Pressure uses Raoult’s law to explain.
  2. Partial Pressure contains dimensionless values, while vapour pressure is used to express it in Pascal.
  3. When we apply pressure on the mixture of gases at the same time, we call it partial pressure. On the other hand, if pressure is applied to the liquid vapour, we call it vapour pressure.
  4. Partial Pressure is used to exert pressure on individual gases with different gases and also at different temperatures. In contrast, vapour pressure is used to exert condensed gas when the temperature gets cooled.
  5. There is a very minute difference in their symbol. We use p to indicate partial pressure. On the other hand, we use p* to indicate vapour pressure.
Difference Between X and Y 2023 05 05T170644.945
References
  1. https://ceramics.onlinelibrary.wiley.com/doi/abs/10.1111/j.1151-2916.1984.tb19701.x
  2. https://www.sciencedirect.com/science/article/pii/0040603177850193

Last Updated : 14 July, 2023

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