What is the delta Hvap of a liquid that has a vapor pressure of 612 torr at 77.6 degrees C and a boiling point of 94.9 degrees C at 1 atm

To determine the delta Hvap (heat of vaporization) of a liquid, you need to know its vapor pressure at a particular temperature and its boiling point at standard atmospheric pressure (1 atm).

Given:
Vapor pressure at 77.6 degrees C = 612 torr
Boiling point at 1 atm = 94.9 degrees C

To calculate the delta Hvap, follow these steps:

Step 1: Convert the given vapor pressure to atm.
To convert torr to atm, divide the value by 760.
Thus, the vapor pressure at 77.6 degrees C becomes 612/760 = 0.805 atm.

Step 2: Calculate the difference in temperature.
The difference in temperature is the boiling point at 1 atm minus the temperature at which the vapor pressure was given:
94.9 degrees C - 77.6 degrees C = 17.3 degrees C.

Step 3: Use the Clapeyron equation to calculate the delta Hvap:
The Clapeyron equation is: ln(P1/P2) = (-delta Hvap / R) * (1/T1 - 1/T2), where:
P1 = vapor pressure at the known temperature (0.805 atm)
P2 = vapor pressure at the boiling point at 1 atm (1 atm)
T1 = known temperature (77.6 degrees C + 273.15) in Kelvin
T2 = boiling point at 1 atm (94.9 degrees C + 273.15) in Kelvin
R = universal gas constant (8.314 J/(mol·K))

Step 4: Rearrange the equation to solve for delta Hvap:
delta Hvap = -R * (1/T1 - 1/T2) * ln(P1/P2)

Calculating the values:
T1 = 77.6 degrees C + 273.15 = 350.75 K
T2 = 94.9 degrees C + 273.15 = 368.05 K

Plugging in the values:
delta Hvap = -8.314 J/(mol·K) * (1/350.75 K - 1/368.05 K) * ln(0.805/1)

Solving the equation will give you the delta Hvap in J/mol.