1. What is Water Vapor Pressure?

Definition: Vapor pressure is the pressure exerted by water vapor in equilibrium with its liquid or solid phase at a given temperature.

Purpose: Understanding vapor pressure is crucial for meteorology, chemical engineering, HVAC design, and many industrial processes.

2. How Does the Calculator Work?

The calculator uses the Antoine equation:

Where:

• \( P \) — Vapor pressure (mmHg)
• \( T \) — Temperature (°C)

Explanation: This empirical equation relates the vapor pressure of water to temperature and is valid for temperatures between 1°C and 374°C.

3. Importance of Vapor Pressure Calculation

Details: Vapor pressure determines evaporation rates, boiling points, and is essential for humidity calculations and phase equilibrium predictions.

4. Using the Calculator

Tips: Enter the temperature in °C. The calculator works best for temperatures between 1°C and 374°C (the critical point of water).

5. Frequently Asked Questions (FAQ)

Q1: Why is vapor pressure important?
A: It determines when water will boil, how quickly it evaporates, and affects weather patterns and industrial processes.

Q2: What are typical vapor pressure values?
A: At 20°C it's about 17.5 mmHg, at 100°C it's 760 mmHg (1 atm, the boiling point).

Q3: How does temperature affect vapor pressure?
A: Vapor pressure increases exponentially with temperature - higher temperatures mean much higher vapor pressures.

Q4: What's the difference between mmHg and other pressure units?
A: 1 mmHg = 1 torr ≈ 133.322 Pa. This unit is traditional for vapor pressure measurements.

Q5: Can this formula be used for ice?
A: No, this version of the Antoine equation is for liquid water. Ice has different vapor pressure characteristics.