PCHEM Workshop 2 Notes

First 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! I know the cursive can get a bit sloppy at times, especially when I’m trying to write quickly!

If you want to contact me for more information/ any clarification/ to start a study group/ need talk to someone… please comment below, DM me on Instagram, or send an email by clicking this link, the icon in the top right corner, or manually typing out breealbright@gmail.com.

FIRST WORKSHOP WITH DINELI | September 3, 2019

Be sure to check Dineli’s page as she mentioned that she would upload some of her notes online. These are not the complete answers for the problem set. Make sure you plug and chug to get the individual answers!

REVIEW OF EQUATIONS AND CONCEPTS

I popped into the workshop just about five minutes late because I’m taking classes for the first time in a couple of years and I forgot that rush hour is a thing, since I commute across a couple of highways. So forgive me for missing out on some notes!

When I got in, Dineli was reviewing the equations and concepts that would be needed to solve this problem set. She derived the equations so she wouldn’t need to do it again while working through the problems. I’m not sure if we would need to write out the derivation in our answers or not, but it may be helpful to derive this on your own or at least review them enough to understand it conceptually.

It is worth noting that Dineli posted this review on her website, so check it out to see all of the notes! I didn’t get to write it all down, and I may have copied something down incorrectly while rushing to keep up.

PROBLEM 1 – ISOTHERMAL EXPANSION

A 0.400 mol sample of an ideal gas expands isothermally from T = 300 K and V = 1.00 L to V = 3.00 L.

1 a) How much work does the gas do if the expansion is into an evacuated space (vacuum)? 1 b) How much work does the gas do if the expansion is done against an external pressure of 3.00 atm? 1 c) What is the maximum possible work done by the gas? 1 d) Draw a P-V sketch to illustrate parts a, b, and c in a similar fashion to Figs. 19.2 – 19.4 of the textbook.

PROBLEM 2 – ADIABATIC EXPANSION

An automobile tire contains air at 320.×103 Pa at 20.0 ◦C. The stem valve is removed and the air is allowed to expand adiabatically against the constant external pressure of 100.×103 Pa until P = Pexternal. Assume the air is an ideal gas with C¯V = 5/2 R (diatomic). Calculate the final temperature.

PROBLEM 3 – ISOTHERMAL vs. ADIABATIC

3.50 mol of an ideal gas is expanded from 450 K and an initial pressure of 5.00 bar to a final pressure of 1.00 bar, and C¯P = 5/2 R. Calculate w for the following two cases. 3 a) The expansion is isothermal and reversible. 3 b) The expansion is adiabatic and reversible. 3 c) Give a physical explanation as to why the result to part (b) is different than that of part (a).

PROBLEM 4

One mole of an ideal gas with C¯ V = 3/2 R is subjected to two successive changes in state: (1) From 25.0◦C and 100. × 103 Pa, the gas is expanded isothermally against a constant pressure of 20.0×103 Pa to twice the initial volume; (2) the gas is cooled at constant volume from 25.0◦C to −25.0◦C. Calculate q, w, ∆U, and ∆H for each of the stages and also for the complete process.

Hello again and thank you for checking out my notes and my website! I’m glad I can help another student in some sort of way. I’ve been in a position where I balanced school, work, clubs, extracurriculars, relationships, friendships, fitness, etc. and it was HARD and I remember how much of a struggle it was to keep up.

Everyone in university seems to be a part of the “hustle culture” of today where we’re doing more things than there are hours in the day and I just want to help people get through it. I just ask that you be kind to yourself and others in return. 🙂 Have a great day, good luck studying, and keep it up! You’re doing great.

Feel free to reach out if you need anything! ~Bree

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