It's a semi-empirical formula describing the relation between vapor pressure and temperature. The Antoine equation is derived from the Clausius–Clapeyron relation. For temperatures higher than 100 ☌, the values start to differ significantly and the Antoine equation is usually the most accurate one. The Tetens equation works well for 0-50 ☌ range, but Buck beats all of them, for every checked value. T (☌)Īs you can notice, the Antoine equation is reasonably accurate for higher temperatures, but the low ones are calculated with quite a big error. The reference values come from Lide table with vapor pressure of water (all pressures given in kPa). The table below shows the comparison of the accuracies between different formulas, for several temperatures from 0-100 ☌ range (32-212☏). You can also use another equation, called the Goff-Gratch formula, but as it's more complicated (and approximately as accurate as Buck formula), we didn't implement it in our vapor pressure of water calculator. Buck formula, also known as Arden Buck equationīuck_pressure = 0.61121 * e^.Magnus formula, also known as August-Roche-Magnus or Magnus-Tetens equation.Jump to the next section to read more about the constants in the Antoine formula. The temperature T is expressed in degrees Celsius and the vapor pressure P is in mmHg. Simple_pressure = e^(20.386 - (5132 / (temperature + 273)), where vapor pressure is expressed in mmHg and temperature in kelvins.Īntoine_pressure = 10^ In our calculator you'll find implemented: The most well known and established is the Antoine equation, but other methods also exist (and they perform better in typical conditions). This can be useful for determining what the vapor pressure of a substance will be at any given temperature, which can then be used to determine its dew point.There are many different formulas thanks to which you can calculate the vapor pressure of water. The Clausius-Clapeyron equation is a thermodynamic relationship that predicts the vapor pressure of water at different temperatures. This can also be referred to as heat of vaporization or heat required to convert 1 mole of a substance from the liquid phase to its gaseous state. The enthalpy of vaporization is the enthalpy change when a substance changes from its liquid phase to its gaseous state (i.e., boiling). Now that you know what the vapor pressure is, let’s look at the enthalpy of vaporization. The main reason this rule is so important? It helps us understand how different things react during combustion processes like explosions or being lit on fire… What is the enthalpy of vaporization? This means that if you know how much gas or liquid can be dissolved into another substance at one atmosphere and given temperature, then you also know how much it would expand as you raise it closer to room temperature-and vice versa! In its simplest form, the Clausius-Clapeyron equation states that for every degree Celsius increase in temperature, a given amount (usually one atmosphere) added to its pressure will cause an additional drop in temperature. The Clausius-Clapeyron equation was developed by German physicist Rudolf Clausius and French mathematician Benoît Paul Émile Clapeyron in 1850. If you want to learn more about the vapor pressure of water you can check out our Vapor Pressure of Water Calculator.Ī vapor pressure chart is a graphical representation of the Clausius-Clapeyron equation, which is used to calculate the vapor pressure of a liquid. The pressure exerted by a saturated liquid (at its boiling point) is known as saturation vapor pressure and it increases with an increase in temperature until all molecules escape from the solution as gas, thus drying out the liquid completely and producing an unsaturated vapor state.
It depends only on the composition, temperature, and any impurities in the substance.
The equilibrium vapor pressure of substances is an intrinsic property that is independent of the presence or absence of liquid. Vapor pressure is the pressure exerted by a vapor in equilibrium with its condensed phases at a given temperature.
#Pressure chemistry calculator how to#
In this article, we’ll look at how to calculate the vapor pressure of an ideal gas and apply that knowledge in order to predict which liquids will evaporate under certain conditions (such as when placed on a hot surface). The vapor pressure of a liquid is affected by temperature and ambient pressure, with higher temperatures leading to higher vapor pressures. A liquid will evaporate if it is at a temperature where its vapor pressure is greater than the surrounding air.
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