Vapor Pressure Calculator
Calculate vapor pressure at a new temperature using the Clausius-Clapeyron equation.
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Enter a known vapor pressure P1 at temperature T1, the target temperature T2, and the enthalpy of vaporization. The calculator uses the Clausius-Clapeyron equation to find the vapor pressure at the new temperature.
About the Vapor Pressure Calculator
The Clausius-Clapeyron equation describes how vapor pressure varies with temperature. It is derived from thermodynamic principles and is widely used to predict boiling points at different pressures, estimate enthalpy of vaporization, and understand phase transitions.
Frequently Asked Questions
What is the Clausius-Clapeyron equation?
It relates vapor pressure to temperature: ln(P2/P1) = (-delta Hvap / R)(1/T2 - 1/T1). It assumes delta Hvap is constant over the temperature range, which is approximately true for moderate ranges.
What is delta Hvap for water?
The enthalpy of vaporization of water is approximately 40,700 J/mol (40.7 kJ/mol) at its normal boiling point of 373 K. This value decreases slightly at higher temperatures.
What happens to vapor pressure as temperature increases?
Vapor pressure increases exponentially with temperature. This is why liquids evaporate faster when heated and why boiling occurs when vapor pressure equals atmospheric pressure.