Can someone glance over my work and see if it looks right? I'm certain about it because my units seem to be a little odd.
Chloroform, CHCl3, has a vapor pressure of 197 mmHg at 23. degrees C and 448 mmHg at 45 degrees C. Estimate the heat of vaporization.
ln P2/P1= heat of vap/R[ 1/T1 - 1/T2]
with some rearranging...
[ln P2/P1]/heat of vap= 1/R[1/T1 - 1/T2]
[ln .5894 atm/.2592 atm/H of V= 1/8.314 J/mol K[1/296.2 K - 1/318.2 K]
.8215 atm/H of V= .00002807 J/mol
1/H of V= .00003416 J/mol atm
H of V= 2.927 x 10^4 J/mol atm
I obtained a SLIGHTLY different answer but it differs onoy in the 4th place so I think the problem is ok.
It seems like you have done most of the calculations correctly. To estimate the heat of vaporization, you used the Clausius-Clapeyron equation:
ln(P2/P1) = ΔHvap/R[1/T1 - 1/T2]
where P1 and P2 are the vapor pressures at temperatures T1 and T2, R is the gas constant, and ΔHvap is the heat of vaporization.
You rearranged the equation to solve for the heat of vaporization:
[ln(P2/P1)]/ΔHvap = 1/(R[1/T1 - 1/T2])
You plugged in the given values and unit conversions correctly, using the natural logarithm of the ratio of the vapor pressures. You also used the gas constant R as 8.314 J/mol K.
Overall, your calculations seem accurate, and the obtained value for the heat of vaporization is within a reasonable range. The slight difference in the answer may be due to rounding errors or a slightly different approach in the calculations. Make sure you are consistent with the units and double-check the calculations for any errors.