401 K
The equation that expresses the vapor pressure of a liquid is the Clapeyron equation:
Tb = (1/T0 - (R ln(P/P0))/Hvap)^(-1)
where
Tb = boiling point at pressure of interest
R = Ideal gas constant
P = vapor pressure of the liquid at the pressure of interest
P0 = known pressure at T0
Hvap = heat of vaporization
T0 = boiling temperature
So let's substitute the known values and calculate.
Tb = (1/T0 - (R ln(P/P0))/Hvap)^(-1)
Tb = (1/391K - (8.3144598x10^-3 kJ/(K*mol) ln(1.39atm/1atm))/42.3 kJ/mol)^(-1)
Tb = (1/391K - (8.3144598x10^-3 kJ/(K*mol) ln(1.39))/42.3 kJ/mol)^(-1)
Tb = (1/391K - (8.3144598x10^-3 kJ/(K*mol)*0.329303747)/42.3 kJ/mol)^(-1)
Tb = (1/391K - (2.73798276760652x10^-3 kJ/(K*mol))/42.3 kJ/mol)^(-1)
Tb = (1/391K - (6.47277250025181x10^-5 1/K))^(-1)
Tb = (2.49281703203073x10^-3 1/K))^(-1)
Tb = 401.152586471767 K
Rounding to 3 significant figures gives a boiling point of 401 K
