Pressure of water vapour is given by
The vapor pressure of water is the pressure at which water vapor is in thermodynamic equilibrium with its condensed state.
ln(P1/P2) = (ΔHvap/R)((1/T2) - (1/T1))
ΔHvap: The enthalpy of vaporization of the liquid.
• R: The real gas content, or 8.314 J/(K × Mol).
• T1: The temperature at which the vapor pressure is known (or the starting temperature.)
• T2: The temperature at which the vapor pressure is to be found (or the final temperature.)
• P1 and P2: The vapor pressures at the temperatures T1 and T2, respectively.