PCHEM Workshop 3 Notes
Third workshop with Dineli for Physical Chemistry (CHEM 3321) with Dr. Nielsen at UT Dallas!
To anyone reviewing my notes: Please feel free to reach out if you need any clarification on anything I wrote! Writing in a ballpoint erasable pen, rather than a fountain pen now, so I’m writing in print instead of cursive. It looks more neat, but some handwriting may be iffy! Reach out if you need clarification. 🙂
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WORKSHOP WITH DINELI | September 10, 2019
Be sure to check Dineli’s page for her notes online. These are not the complete answers for the problem set. Make sure you plug and chug to get the individual answers!
PROBLEM 1 – DERIVATIVE MANIPULATIONS
I can’t format the equations in the block editor for my website, so I’ll just copy the question and paste it below!
This was pretty straightforward. You could probably just copy what I have posted here for your response, as it is sufficient proof that the left side of the equation is equal to the right side of the equation.
PROBLEM 2 – CONDENSATION
A sample of 2.00 mol of CH3OH(g) is condensed isothermally and reversibly to liquid at 64 ◦C. The standard enthalpy of vaporization of methanol at 64 ◦C is 35.3 kJ/mol. Find w, q, ∆U, and ∆H for this process.
PROBLEM 3 – HEAT CAPACITY
When 3.00 mol O2(g) is heated at a constant pressure of 3.25 atm, its temperature increases from 260 K to 285 K. Given that the molar heat capacity of O2(g) at constant pressure is 29.4 J K^−1 mol^−1, calculate q, ∆U and ∆H.
PROBLEM 4 -ENTHALPIES
a) The standard enthalpy of combustion of cyclopropane is -209 kJ/mol at 25 ◦C. From this information and enthalpy of formation data for CO2(g) and H2O(g), calculate the enthalpy of formation of cyclopropane.
b) The enthalpy of formation of propene is +20.42 kJ/mol at 25 ◦C. Calculate the enthalpy of isomerization of cyclopropane to propene.
PROBLEM 5 – ENTHALPY FROM THE THERMODYNAMIC CYCLE
Given the following data: heat capacity of ice: 37.7 J K−1 mol−1 heat capacity of water: 75.3 J K−1 mol−1 ∆H◦ f (water) = -285.83 kJ mol−1 at 298 K ∆H◦ f (ice) = -291.83 kJ mol−1 at 298 K
a) For water freezing at 298 K, compute the enthalpy change using the heats of formation data (express in J mol−1 ). b) For water freezing at -5 ◦C, draw a thermodynamic path connecting the initial state (water at -5 ◦C) to the final state (ice at -5 ◦C) making use of all the given data. c) Using this path, calculate the enthalpy of water freezing at -5 ◦C (express in J mol−1) d) Predict at what temperature the freezing of water changes from exothermic to endothermic. e) Is the temperature you predicted in part (d) experimentally realizable? What is the record low temperature for supercooled (liquid) water?
A note on part (D) and (E): some chick busted in the room at 6:57 and said, “We have a meeting in three minutes.” (level 100 disrespecc) so Dineli did her best to get through the remaining parts of the homework in three minutes. I recorded a video of her talking through it, but I’m not sure if I can post that here since there are some laws about taking photos and recording videos in the classroom + posting them online.
Dineli said she’d try to post it on her website. I that saw some classmates were able to snag a copy of part (D) and put it up on the GroupMe. Whenever I go through the homework myself, I’ll upload it here as well. It might not be until tomorrow night though… If you need to be added to the GroupMe, hit me up!
Good luck on your first round of exams in all of your classes, everyone! You’re going to do great and it’s not the end of your career if you don’t. Keep it up! 🙂
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