A certain liquid has a vapor pressure of 92.0 Torr at 23.0 °C and 313.0 Torr at 45.0 °C. Calculate the value of ΔH°vap for this liquid.

Given Data:

P 1=92 torr

P 2=313

T 1=296 k

T 2=318

Hvap = 47900 Joules

R=1.99 cal/mole-k

Using Clausius-Clapeyron equation:

logP2/P1 = delta H / (2.303*R) * (1/T1-1/T2)

log 313/92=0.53

2.303*R = 2.303*1.99

= 4.5829 cal/mole-k

1/T1-1/T2=1/296 - 1/318

= 0.0000233

delta H = 0.53*4.5829/0.000233

delta H = 10424.622 cal