How To Calculate Vapor Pressure Of H2o

Magnus Formula:

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

Vapor Pressure (e_s):

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1. What is the Magnus Formula?

The Magnus formula is an empirical relationship that calculates the saturation vapor pressure of water over liquid water as a function of temperature. It provides an accurate estimation of water vapor pressure in meteorological and environmental 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 (°C)
6.112 — Reference vapor pressure at 0°C (hPa)
17.67 and 243.5 — Empirical constants

Explanation: The formula describes how water vapor pressure increases exponentially with temperature, following the Clausius-Clapeyron relationship.

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 water vapor.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What is the physical significance of vapor pressure?
A: Vapor pressure represents the pressure exerted by water vapor in equilibrium with its liquid phase at a given temperature.

Q2: How does vapor pressure relate to humidity?
A: Relative humidity is the ratio of actual vapor pressure to saturation vapor pressure at the same temperature, expressed as a percentage.

Q3: Why use the Magnus formula instead of other equations?
A: The Magnus formula provides a good balance between accuracy and computational simplicity for most practical applications.

Q4: What are typical vapor pressure values?
A: At 0°C: 6.11 hPa, at 20°C: 23.39 hPa, at 40°C: 73.78 hPa. Vapor pressure approximately doubles with every 10°C temperature increase.

Q5: Are there limitations to the Magnus formula?
A: The formula is empirical and may have reduced accuracy at extreme temperatures or in very dry conditions. Different coefficient sets exist for specific temperature ranges.