Vapor Pressure of Water Calculator is a free online tool that displays the vapor pressure of the water at a given temperature. CoolGyan’S online vapor pressure of Water calculator tool performs the calculation faster and it displays the vapor pressure in a fraction of seconds.

## How to Use the Vapor Pressure of Water Calculator?

The procedure to use the vapor pressure of water calculator is as follows:

**Step 1:** Enter the temperature in the input field (Example: 49°C)

**Step 2:** Now click the button “Solve” to get the vapor pressure

**Step 3:** Finally, the vapor pressure of water for the given temperature will be displayed in the output field (I.e., Vapor pressure of water at 49°C = 87.81748 mm Hg)

### What is Meant by Vapor Pressure of Water?

The vapor pressure of a water is defined as the pressure at which the gas phase and the liquid phase are in the equilibrium state. If the water has high surface tension, it means that the water has low vapor pressure. In a closed container, the vapor pressure is constant. The vapor pressure changes with the nature of the substance and the surrounding temperature. It means that if the temperature is high, the molecules possess enough energy to escape from the solid or liquid objects, which leads to high vapor pressure. Similarly, the substance with relatively weak force should have a high vapor pressure.

**Also, check:** Liquid State Vapor Pressure

The formula to calculate the vapor pressure of water is given as

\(P=10^{A- [B/(C+T)]}\)

Here,

P is the water vapor pressure

T is the temperature

A, B, C are the Antoine constant of water

Note that the Antoine constant of water will change according to the temperature. If the temperature ranges from 1 to 100-degree Celsius, the value of Antoine constants are A = 8.07131, B = 1730.63, and C = 233.426. If the temperature of the water ranges from 99 to 374-degree Celsius, the constant value becomes A=8.14019, B=1810.94 and C=244.485.

**Read: **Physical and Chemical Properties of Water

### Vapor Pressure of Water Example

**Example: **

Find the vapour pressure of water if the temperature is 49°C

**Solution:**

Given that, temperature = 49°C

Since the temperature ranges from 1 -100°C, the constant values of A, B, C are:

A = 8.07131

B = 1730.63

C = 233.426

Now, substituting the values in the formula \(P=10^{A- B/(C+T)}\) , we get

\(P=10^{8.07131- 1730.63/(233.426+49)}\)

\(P=10^{8.07131- 1730.63/282.426}\) \(P=10^{8.07131- 6.127729}\) \(P=10^{1.943581}\)P= 87.81748

Hence, the vapor pressure of water at 49°C is 87.81748 mm Hg