Difference Between Partial Pressure and Vapor Pressure

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 they are common in all the curriculums across the countries. 

Partial Pressure vs Vapor Pressure

The main difference between Partial Pressure and Vapor Pressure is that Partial Pressure uses individual gas, and they are alone, while Vapor Pressure contains pressure exerted by the vapor in the condensed liquid state. Partial pressure uses the pressure to exhale the gas. But vapor pressure uses an equilibrium phenomenon. And their state of work differs a lot.

Partial Pressure vs Vapor Pressure

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 upon the problem we deal with.

We can simply explain the concept of vapor 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 vapor 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 Between Partial Pressure and Vapor Pressure

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

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 inside it 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 used to pressure in two ends and the regions connected. The partial pressure in liquid can be defined as that 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. 

What is Vapor Pressure?

When we placed a liquid in a vessel, it will get heated, and the molecules will be seen, and they will move in different directions with 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 Vapor.

Vapor Pressure can be sometimes called Vapor Equilibrium Pressure. There are many characteristics of vapor pressure. Temperature acts as the main aspect that affects vapor pressure. When we raise the temperature, the vapor pressure will also rise. The evaporation process will depend on two following factors such 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 vapor pressure. It is related to evaporation. It is again used in both chemistry and physics. Diethyl Ether is the highest vapor pressure in Chemistry. Molecules that contain the strongest intermolecular forces are considered to be the lowest vapor pressure in Chemistry.

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 vapor 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-vapor, we call it vapor pressure.
  4. Partial Pressure is used to exert pressure of individual gases with different gases and also at different temperatures. While vapor 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 vapor pressure.


Both partial pressure and vapor pressure are used in science in the field of physics and chemistry. You will be required to study it in your higher studies as well. There you will be given case studies and documents to deal with. It is one of the important concepts in science. It is a basic concept, and every student should have a clear understanding to proceed further.

Even you plan to study physics in your higher studies, it will be required to have a piece of knowledge of that concept and vice versa. Using the formula for these two pressures, we would be able to solve many problems and further concepts in science. This concept would be very interesting if we use any examples to learn. It will help us to understand, and we will never forget it in this lifetime. 


  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

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