How To Calculate Vapor Pressure Of Water

Magnus Formula:

\[ e_s = 6.112 \times \exp\left(\frac{17.67 \times T}{T + 243.5}\right) \]

Saturation Vapor Pressure (e_s):

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1. What is the Magnus Formula?

The Magnus formula is an empirical relationship that describes the saturation vapor pressure of water over liquid water as a function of temperature. It provides an accurate estimation of vapor pressure for meteorological and scientific applications.

2. How Does the Calculator Work?

The calculator uses the Magnus formula:

\[ e_s = 6.112 \times \exp\left(\frac{17.67 \times T}{T + 243.5}\right) \]

Where:

\( e_s \) — Saturation vapor pressure (hPa)
\( T \) — Temperature in degrees Celsius (°C)
\( \exp \) — Exponential function (e^x)

Explanation: The formula calculates the maximum amount of water vapor that air can hold at a given temperature before condensation occurs.

3. Importance of Vapor Pressure Calculation

Details: Accurate vapor pressure calculation is essential for weather forecasting, humidity measurement, climate studies, and various industrial processes involving air-water interactions.

4. Using the Calculator

Tips: Enter temperature in degrees Celsius. The formula is valid for temperatures between -50°C and 100°C, with best accuracy between 0°C and 60°C.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between vapor pressure and saturation vapor pressure?
A: Vapor pressure is the actual pressure exerted by water vapor in air, while saturation vapor pressure is the maximum possible vapor pressure at a given temperature before condensation occurs.

Q2: Why is 6.112 used in the formula?
A: 6.112 hPa is the saturation vapor pressure at 0°C, serving as the base constant in the Magnus formula.

Q3: How does temperature affect vapor pressure?
A: Vapor pressure increases exponentially with temperature. Warmer air can hold significantly more water vapor than colder air.

Q4: Are there limitations to the Magnus formula?
A: The formula is empirical and works best for temperatures between 0°C and 60°C. For extreme temperatures or high precision applications, more complex equations may be needed.

Q5: How is relative humidity calculated from vapor pressure?
A: Relative humidity = (actual vapor pressure / saturation vapor pressure) × 100%. This calculator provides the saturation vapor pressure needed for such calculations.