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Vapor Pressure Calculator

Find the vapor pressure of liquids and mixtures by entering the required inputs in the following calculator.

Clausius-Clapeyron Equation

Initial Temperature:

k ▾

Final Temperature:

k ▾

Initial Pressure:

Pa ▾

Enthalpy of Vaporization:

J ▾

Raoult's Law

Mole Fraction:

Pressure of the Solvent:

Pa ▾

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Vapor Pressure Calculator

Use the vapor pressure calculator to determine the precise vapor pressure of a substance or a mixture for your chemistry experiments.

What Is Meant By Vapor Pressure?

This is the pressure exerted by the molecules of a substance that is placed inside a closed system. It occurs when the vaporization and condensation are happening at the same time.

Vapor Pressure is an essential property that is widely used in the field of chemistry because it allows predicting the behavior of substances under various types of conditions.

The three main factors that affect vapor pressure are:

Temperature
Surface area
Intermolecular Force

Vapor Pressure Formula:

Use the Clausius-Clapeyron equation below to find the vapor pressure at a specific temperature:

\( \ln \left( \frac{P_2}{P_1} \right) = - \frac{\Delta H_{vap}}{R} \left( \frac{1}{T_2} - \frac{1}{T_1}\right) \)

Where

T₁ = Initial temperature measured in Kelvin
T₂ = Final temperature
P₁ = Initial pressure
P₂ = Final pressure
ΔH = Molar enthalpy of vaporization
R = Gas constant which is equal to 8.3145 J/mol⋅K

You can also use Raoult's Law to find the vapor pressure:

\( P_{\text{solution}} = X_{\text{solvent}} \cdot P^{\circ}_{\text{solvent}}\)

Where

\( P_{\text{solution}}\) is the vapor pressure of a solution
\( P_{\text{solvent}}\) represents the solvent vapor pressure
\(X_{\text{solvent}}\) is the mole fraction of the solvent

How To Calculate Vapor Pressure?

Clausius Clapeyron Equation:

Follow the below-mentioned steps to calculate the vapor pressure:

First of all, determine the value of the temperature at which you want to find the pressure
Get the value of the initial pressure
Determine the value of heat of vaporization (\(\Delta H_{vap}\)) of the specific substance
Now convert the temperature to kelvin by adding 273.15 to the value of temperature, if your temperature is in Celsius
Add these values to the above-mentioned vapor pressure formula and you will get the value of vapor pressure

Raoult's Law:

Determine the mole fractions of the components that are available in a mixture
Find the vapor pressure (P) of the component
If the mixture has multiple components then find the vapor pressure of each component
Sum the vapor pressures of all components to get the total vapor pressure

Vapor Pressure Example:

Suppose you have a solution that has a solute mole fraction of 0.6. The vapor pressure of water is 16.358 mmHg at 23 °C. How to find vapor pressure of the solution.

Solution:

\(X_{\text{solvent}}\) = 1.0000 − 0.6 = 0.4

Put the values in the vapor pressure equation of Raoult’s Law:

\( P_{\text{solution}} = X_{\text{solvent}} \cdot P^{\circ}_{\text{solvent}}\)

x = (0.4) (16.358)

x = 6.5432 mmHg

Common Substances:

In the following table we have mentioned various compounds, their boiling point, normal temperature and heat of vaporization.

Compound	Boiling point, at normal pressure	Heat of vaporization
(K)	(°C)	(°F)	(kJ/mol)	(J/g)
Acetone	329	56	133	31.300	538.9
Aluminium	2792	2519	4566	294.0	10500
Ammonia	240	−33.34	−28	23.35	1371
Butane	272–274	−1	30–34	21.0	320
Diethyl ether	307.8	34.6	94.3	26.17	353.1
Ethanol	352	78.37	173	38.6	841
Hydrogen (parahydrogen)	20.271	−252.879	−423.182	0.8992	446.1
Iron	3134	2862	5182	340	6090
Isopropyl alcohol	356	82.6	181	44	732.2
Methane	112	−161	−259	8.170	480.6
Methanol	338	64.7	148	35.2	1104
Propane	231	−42	−44	15.7	356
Phosphine	185	−87.7	−126	14.6	429.4
Water	373.15	100	212	40.66	2257

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