1. What is Water Vapor Pressure?

Water vapor pressure is the pressure exerted by water vapor in thermodynamic equilibrium with its condensed phases (liquid or solid) at a given temperature in a closed system. It is independent of volume and depends only on temperature.

2. How Does the Calculator Work?

The calculator uses the Antoine equation for water:

Where:

• \( P \) — Vapor pressure (Pa)
• \( T \) — Temperature in Kelvin

Explanation: The equation shows the exponential relationship between temperature and vapor pressure. The result is converted from Pascals to psi for display.

3. Importance of Vapor Pressure Calculation

Details: Vapor pressure is crucial for understanding evaporation rates, boiling points, and designing systems that involve water or steam. It's used in meteorology, HVAC design, chemical engineering, and many industrial processes.

4. Using the Calculator

Tips: Enter the temperature in Celsius between -20°C and 200°C. The calculator will compute the vapor pressure of water at that temperature.

5. Frequently Asked Questions (FAQ)

Q1: Why is vapor pressure independent of volume?
A: In a closed system at equilibrium, vapor pressure depends only on temperature because the rate of evaporation balances the rate of condensation regardless of the system's volume.

Q2: How does temperature affect vapor pressure?
A: Vapor pressure increases exponentially with temperature. Higher temperatures give water molecules more energy to escape the liquid phase.

Q3: What is the boiling point in relation to vapor pressure?
A: The boiling point occurs when the vapor pressure equals the surrounding atmospheric pressure.

Q4: Does this calculator work for salt water or other solutions?
A: No, this calculator is for pure water only. Solutions have lower vapor pressures (Raoult's Law).

Q5: Why is the result in psi?
A: PSI (pounds per square inch) is a common pressure unit in many engineering applications, though the calculation is done in Pascals and converted.