Answered

The vapor pressure of the liquid HF is measured at different temperatures. The following vapor pressure data are obtained: Temperature 270.6K and 287.5K, Pressure 324.5 mmHg and 626.9 mmHG. Calculate the enthapy of vaporization ( delta H vap ) in kJ/mol for this liquid.

Answer :

Answer:

Enthalpy is 44.95 kJ/mol

Solution:

As per the question:

Temperature, T = 270.6 K

Temperature, T' = 287.5 K

Pressure, P = 324.5 mmHg

Pressure, P' = 626.9 mmHg

Now,

To calculate the enthalpy, we make use of the Clausius-Clapeyron eqn:

[tex]ln\frac{P}{P'} = \frac{\Delta H}{R}(\frac{1}{T'} - \frac{1}{T})[/tex]

where

[tex]\Delta H = Enthalpy[/tex]

R = Rydberg's constant

Substituting suitable values in the above eqn:

[tex]ln\frac{324.5}{626.9} = \frac{\Delta H}{8.31447}(\frac{1}{287.5} - \frac{1}{270.6})[/tex]

[tex]- 0.658 = \frac{\Delta H}{8.31447}(\frac{1}{287.5} - \frac{1}{270.6})[/tex]

[tex]\Delta H = 44.95\ kJ/mol[/tex]

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