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Partial Pressure Formula:
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When a gas is collected over water, the total pressure measured is the sum of the partial pressure of the dry gas and the vapor pressure of water. The partial pressure of the dry gas is calculated by subtracting the water vapor pressure from the total pressure.
The calculator uses the formula:
Where:
Explanation: This calculation is essential when gases are collected over water, as water vapor contributes to the total pressure measurement.
Details: Accurate determination of partial pressure is crucial for gas law calculations, chemical reactions, and understanding gas behavior in various scientific and industrial applications.
Tips: Enter the total pressure and water vapor pressure in Pascals (Pa). Both values must be positive, and the total pressure must be greater than or equal to the water vapor pressure.
Q1: Why do we subtract water vapor pressure?
A: When a gas is collected over water, water evaporates and contributes to the total pressure. Subtracting the water vapor pressure gives the true pressure of the dry gas alone.
Q2: How do I find the water vapor pressure?
A: Water vapor pressure depends on temperature. You can find it in standard reference tables or calculate it using appropriate formulas based on the temperature.
Q3: Can this calculation be used for other liquids?
A: Yes, the same principle applies to any liquid over which a gas is collected. You would use the vapor pressure of that specific liquid instead of water.
Q4: What units should I use for pressure?
A: While Pascals (Pa) are used here, you can use any pressure unit as long as you're consistent. Common alternatives include mmHg, atm, or bar.
Q5: What if the gas is soluble in water?
A: For gases that are soluble in water, additional corrections may be needed as some gas may dissolve in the water, affecting the pressure measurement.