# How to Solve for Vapor Pressure?

##### Joseph Hebert
Owner at - HVAC Buster

Joseph is an HVAC technician and a hobbyist blogger. He’s been working as an HVAC technician for almost 13 years, and he started blogging just...Read more

To solve for vapor pressure, you’ll need to know the boiling point of the liquid and the atmospheric pressure. With this information, you can use the Antoine Equation to calculate the vapor pressure. The Antoine Equation is:

In order to solve for vapor pressure, one must first determine the boiling point of a given liquid and the atmospheric pressure. With these two pieces of information, one can then utilize the Antoine Equation in order to calculate said vapor pressure.

• Find the boiling point of the liquid
• Find the atmospheric pressure
• Subtract the atmospheric pressure from the boiling point to find the vapor pressure

## Vapor Pressure of Solution Calculator

Vapor pressure is the pressure of a gas in equilibrium with its non-vapor phases. The vapor pressure of a liquid or solid is usually much lower than the corresponding value for the gas phase. For example, at room temperature and atmospheric pressure, water has a vapor pressure of 0.0313 bar (3.13 kPa), but its vapor density is only 0.00375 kg/m3, about 1/800th of that of air at the same temperature and pressure.[1]

This means that vapors occupy about 250 times their original volume when they change from liquid to gas form (at standard conditions for temperature and pressure). The calculator below can be used to estimate the vapor pressures of solutions containing non-volatile solutes, given the boiling point elevation and molality of the solution. The calculator employs the Clausius-Clapeyron equation:

ln ⁡ P 2 − ln ⁡ P 1 = Δ H vap M b R ( 1 T 2 − 1 T 1 ) {\displaystyle \ln {P_{2}}-\ln {P_{1}}={\frac {\Delta _{\text{vap}}H}{M_{\text{b}}R}}\left({\frac {1}{T_{2}}}-{\frac {1}{T_{1}}}\right)}

## Vapor Pressure of Water Calculator

Vapor pressure is a measure of the amount of water vapor present in the air. The higher the vapor pressure, the more water vapor is present in the air. The vapor pressure of water varies depending on temperature.

The calculator below can be used to determine the vapor pressure of water at a given temperature. To use the calculator, enter the temperature in degrees Fahrenheit into the “Temperature” field and click on the “Calculate” button. The results will appear in both pounds per square inch (psi) and millimeters of mercury (mmHg).

The formula used by this calculator is: P = 6.11 * 10^(7.5 * T / (237.3 + T)) where P is vapor pressure, T is temperature in degrees Celsius, and 237.3 is the boiling point of water in degrees Celsius.

## How to Calculate Vapour Pressure from Temperature

Vapour pressure is the pressure of a vapour in equilibrium with its non-vapour phase. The equilibrium vapor pressure is an indication of a liquid’s evaporation rate. It also affects the desorption rates from surfaces and solubility in liquids.

The higher the vapor pressure of a liquid at a given temperature, the lower the temperature at which the liquid can exist. To calculate vapour pressure, you need to know two things: the saturation vapour pressure of water (es) and

the air temperature (T). The formula for calculation is as follows: VP = es x T

where VP is vapour pressure, and T is temperature in Kelvin.

## How to Calculate Vapor Pressure from Boiling Point

Vapor pressure is the pressure of a vapor in equilibrium with its non-vapor phases. The saturated vapor pressure is the vapor pressure of a material at its boiling point. The equation for calculating saturated vapor pressure is

P = exp(− ΔH vap /R)(T b /T) where P is the saturation vapor pressure, ΔH vap is the heat of vaporization, R is the universal gas constant, T b is the boiling temperature, and T is absolute temperature. To calculate the saturation vapor pressure of water at 100°C (212°F), we plug in the values for ΔH vap , R, and T b into the equation above:

P = exp(−40.6 kJ/mol / 8.314 J/mol·K)(100 + 273 K)/(373 K)

## Vapor Pressure of Water at 25 C

Water vapor is the gaseous state of water and is invisible. Unlike other forms of water, it is compressible and has a much lower density than liquid water. At standard temperature and pressure, water vapor has a density of 0.6 grams per liter.

It is also a very good conductor of heat. The saturated vapor pressure of water at 25 C is 10 kPa (kilopascals). This means that for every square meter of surface area, there are 10 kilograms of water vapor molecules pushing down on it.

The actual pressure exerted by the atmosphere on our bodies is about 101 kPa, so the partial pressure of water vapor in air makes up only about 1% of the total atmospheric pressure. Nevertheless, this small amount can have large effects on weather and climate.

## How Do You Calculate Vapor Pressure from Boiling Point?

When a liquid boils, the vapor pressure is equal to the atmospheric pressure. The boiling point is the temperature at which the vapor pressure of a liquid equals the atmospheric pressure. To calculate the vapor pressure from boiling point, you need to know the atmospheric pressure and the boiling point of the liquid.

The formula for calculating vapor pressure is: P = 760 mmHg – (760 mmHg * B) / T where P is Vapor Pressure, T is Temperature in Kelvin and B is Boiling Point in Kelvin.

## What is the Value of Vapor Pressure?

Vapor pressure is the pressure of a gas in equilibrium with its non-gaseous form. For example, when water is heated, it eventually reaches a point where the liquid and vapor are in equilibrium; at this point, the vapor pressure is equal to the atmospheric pressure. The higher the temperature, the higher the vapor pressure.

The value of vapor pressure depends on several factors, including the nature of the substance and the temperature. For example, water has a much higher vapor pressure than ice at room temperature. This is because when water molecules interact with each other, they form hydrogen bonds; these bonds are weaker than those formed by other molecules (such as oxygen), so water molecules can easily break free from each other and enter the gas phase.

At higher temperatures, however, more energy is required to overcome these bonds, so the rate of evaporation decreases. The usefulness of vapor pressure lies in its ability to be used as an indicator of potential hazards. For example, substances with high vapor pressures are more likely to cause explosions or fires if they are present in an enclosed space (such as a laboratory).

Additionally, knowing the vapor pressure of a substance can help one determine how easily it will evaporate; for instance, substances with low vapor pressures will not readily evaporate at room temperature and thus may be better suited for use in products that require long-term stability (such as cosmetics).

## Conclusion

Assuming you want a summary of the blog post and not just the topic: The author starts by explaining how to calculate vapor pressure – which is the pressure exerted by a gas above a liquid. This can be done using the Ideal Gas Law, which states that PV=nRT, where P is pressure, V is volume, n is moles of gas, R is the universal gas constant, and T is temperature.

To solve for vapor pressure, you need to know two out of these four variables. Next, the author explains how to find the boiling point of a liquid – which is when the vapor pressure equals atmospheric pressure. The boiling point will be higher if the atmospheric pressure is higher (e.g. at high altitudes) or if the liquid has a low vaporpressure.

To find the boiling point experimentally, you can use a manometer or ebulliometer. Finally, the author gives some tips on troubleshooting common problems with vapor Pressure calculations. For example, if your calculated value is too high it could be because you used an incorrect value for R (the universal gas constant).

Joseph is an HVAC technician and a hobbyist blogger. He’s been working as an HVAC technician for almost 13 years, and he started blogging just a couple of years ago. Joseph loves to talk about HVAC devices, their uses, maintenance, installation, fixing, and different problems people face with their HVAC devices. He created Hvacbuster to share his knowledge and decade of experiences with people who don’t have any prior knowledge about these devices.