What is the approximate vapor pressure (to the nearest 50 torr) of H2O at 75 oC?

Question

What is the approximate vapor pressure (to the nearest 50 torr) of H₂O at 75 ^oC?

Answer 1

Vapor pressure of H2O @760 torr and 273K = 459 torr (Wikipedia)

∆Hvap = 40.68 kJ/mol (Wikipedia)

Clausius Clapeyron equation:

ln(P2/P1) = -∆Hvap/R (1/T2 - 1/T1)

P1 = 459 torr

T1 = 273K

P2 = ?

T2 =75ºC + 273 = 348K

∆Hvap = 40.68 kJ/mol

R = 8.314 J/Kmol = 0.008314 kJ/mol

ln(P2/459) = -40.68/0.008314 (1/348 - 1/273)

ln(P2/459) = -4893(0.00287 - 0.00366)

ln(P2/459) = -4893 x -0.000786

ln(P2/459) = 3.85

P2/459 = 1.35

P2 = 618 torr = 600 torr (to the nearest 50 torr)