A certain liquid has a vapor pressure of 92.0 Torr at 23.0 °C and 351.0 Torr at 45.0 °C. Calculate the value of ΔH°vap for this liquid.

There is a specific formula to use for these type of problems.

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

R = 8.314

P1 = 92.0 torr

T1 = 23 C + 273 = 296 K

P2 = 351.0 torr

T2 = 45.0 C + 273 = 318 K

plug the values and solve for the unknown

ln (351.0 / 92.0) = Δvap / 8.314 x (1/296 - 1/318)

Δvap = 47630.6 joules