Question

The smell of fresh cut pine is due in part to the cyclic alkene called pinene. Given the following data of pinene: Vapor pressure (torr) Temperature (K) 760 429 515 415 Calculate the heat of vaporization, ΔHvap, of pinene.

Answer 1

Answer: Heat of vaporization is 41094 Joules

Explanation:

The vapor pressure is determined by Clausius Clapeyron equation:

$ln(\frac{P_2}{P_1})=\frac{\Delta H_{vap}}{R}(\frac{1}{T_1}-\frac{1}{T_2})$

where,

$P_1$= initial pressure at  429 K = 760 torr

$P_2$ = final pressure at 415 K  = 515 torr

= enthalpy of vaporisation = ?

R = gas constant = 8.314 J/mole.K

$T_1$= initial temperature =  429 K

$T_2$ = final temperature = 515 K

Now put all the given values in this formula, we get

$\log (\frac{515}{760}=\frac{\Delta H}{2.303\times 8.314J/mole.K}[\frac{1}{429K}-\frac{1}{415K}]$

$\Delta H=41094J$

Thus the heat of vaporization is 41094 Joules