A certain liquid has a vapor pressure of 92.0 Torr at 23.0 ∘C and 274.0 Torr at 45.0 ∘C. Calculate the value of Δ𝐻∘vap for this liquid. Δ𝐻∘vap= 38.8 kJ/mol

Question

Calculate the normal boiling point of this liquid.

boiling point: ___ ∘C

Answer 1

For these types of problems, we can use the Clausius Clapeyron equation:

ln (P2/P1) = -Ea/R (1/T2 - 1/T1)

P1 = 92.0 torr

P2 = 274torr

T1 = 23º + 273 = 300K

T2 = 45º + 273 = 318K

R = 8.314 J/molK

Ea = ?

ln (274/92) = -Ea/8.314 (1/318 - 1/300)

1.09 = -Ea / 8.314 (0.00314 - 0.00333)

1.09 = -Ea / 8.314 (-0.000193)

1.09 = 0.000193Ea / 8.314

Ea = 46,955 J/mol = 47.0 kJ/mol