Using the vapor pressure data for acetic acid, CH3COOH(l),

Temperature (degrees C)

Vapor Pressure (mmHg)

10.0

6.00

20.0

11.6

30.0

21.3

40.0

37.3

50.0

63.7

 

Here the table is completed.

T (degrees C)

T (Kelvins)

T-1

Pv (mm Hg)

ln (Pv)

10.0

283

0.00353

6.00

1.79

20.0

293

0.00341

11.6

2.45

30.0

303

0.00330

21.3

3.06

40.0

313

0.00319

37.3

3.62

50.0

323

0.00310

63.7

4.15

Now plot the data with ln (Pv) on y-axis and on the T-1 x-axis. After you have plotted the data go to the next page to see the plot.

In the plot above I've plotted the data (ln (Pv) versus T-1). I also did a linear regression on the data to get the equation for the line (the R value is perfect...great professor data!).

Can do determine the delta H of vaporization for ammonia?

Answer;

From the slope of the line in the plot we recall;

slope = ÐÆHovap/R

From the linear regression the slope of the date is equal to Ð5390 K-1;

Substituting;

Ð5390 K-1 = ÐÆHovap/R

In this equation R has a value of 8.314 J mol-1 K-1

ÐÆHovap = Ð5390 K-1 x 8.314 J mol-1 K-1

ÐÆHovap = 44.8 kJmol

Now answer the following two questions;

Use the your plot to determine the temperature at which acetic acid has a vapor pressure of 42.4 mmHg.

Use the your plot to determine the vapor pressure of acetic acid at 13.5 ûC.

Answers to these last two questions.