Chemistry the Enthalpy of Vaporization Questions

Post ID: 2743444

Open a blank excel to build this week's modeling.

1. Assign a tab to each compound or molecule (each molecule from your approved equation) and along the top of the excel organize the following information:

1. Compound or molecule name

2. Gas constant, R

3. Enthalpy of vaporization

4. Clausius-Clapeyron equations (rewrite these yourself)

2. Search the web for your molecules temperature dependent vapor pressure curve data (cite your source). This may not be available on NIST.

Pay attention to the temperature range of the vapor pressure data you are able to find. You will also be referencing the enthalpy of vaporization and if these temperature range/values do not agree that may lead to an increased percent error.

3. Create temperature (K) and pressure (kPa) columns with proper labels and units, you can create several columns in order to convert units if needed here.

4. Create and calculate inverse temperature and natural log pressure columns.

5. Plot lnP vs 1/T and add a trendline. Format your graph correctly and completely and make sure your trendline is also formatted correctly.

6. Record the value of your slope into a single cell.

7. Calculate your molecules enthalpy of vaporization based on the slope from your plot. You should be calling on the cell from step 6 in your formatted equation.

8. Calculate a percent difference between your calculated enthalpy of vaporization and the referenced value. Make sure you are referencing the correct molecule; google searching "hydrogen gas" for example returns a top hit for atomic hydrogen and this will lead to a large percent error!

Repeat for each molecule.

Questions

What are the three compounds/molecules you modeled this week? Where did you find their vapor pressure data?
Why don’t we specify that the enthalpy of vaporization is standard or not? Do we consider temperature dependence?
What were the percent differences for each of your gasses heat of vaporization compared to the referenced values?
Which would we expect to have a higher vapor pressure, octane or octanol? Why?
Describe how you could determine a molecule’s heat of vaporization if the only information you knew were a set of experimental temperature dependent vapor pressures.

https://youtu.be/oc0ypeDELb0

https://www.youtube.com/watch?v=bV9hJm3JXOM

https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Equilibria/Physical_Equilibria/Phase_Diagrams_for_Pure_Substances

https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Physical_Properties_of_Matter/States_of_Matter/Phase_Transitions/Vapor_Pressure