Question

What is meant by this calculus-ish formula (in regards to PV=nRT)

Answer 1

Is it enthalpy as a function of pressure at constant Temperature?

Answer 2

yep those deltas mean partial derivatives

Answer 3

So my understanding of partial derivatives was that you take out the bottom variable in the equation. Is that right? Plus, is it possible to do this with PV=nRT? I have a problem that has \[(deltaV/deltaT)_{p}\] and it makes no sense to me

Answer 4

no the variable at the bottom (you mean outside of the bracket, right?) is held constant, not taken out

Answer 5

i mean you only use PV=nRT if you need to use it, theres tons of other formulas you need in thermo

Answer 6

I meant inside the bracket

Answer 7

Clearly I only got threw calculus by the skin on my nose, and my Chem professor isn't helping at all

Answer 8

no you don't take it out. Damn you got some work ahead, son!
lol i'm taking thermo at the moment myself, whats the question il see if can help you

Answer 9

Well really it's a lab report. We had to find the enthalpy of a chemical (which I was able to calculate just fine) but now we have to correct that number for constant temp, constant pressure, and ideality of the gas, so that we can get the standard enthalpy.

Answer 10

This is the equation he gives us to correct for constant pressure

Answer 11

Where alpha is equal to all this jazz. He "explains" it with this paragraph

Answer 12

oh yeah, alpha would just be a coefficient to correct for the heat capacity not being constant over the range of temp

Answer 13

Wrong paragraph.

Answer 14

i'm not completely sure, i have been neglecting this class to be honest. but it seems that you have to integrate the change in volume as a function of temperature, keeping the pressure at a single value

Answer 15

That's what I was thinking, but the point of this equation is to standardize delta H from about 30 bar down to 1 bar. So am I supposed to use 30 or 1 or am I just supposed to stop overthinking things?

Answer 16

apparently, alpha = 1/T

Answer 17

http://www.files.chem.vt.edu/chem-dept/marand/HW1MSES.pdf look at the 2nd page

Answer 18

Well thats... Strange...

Answer 19

If alpha is =1/T and that is multiplied by T then that section is equal to 1. V(1-1) = 0. Then deltaH/deltaP, constant T = 0?

Answer 20

hm yeah that doesn't make sense. you should try integrating it

Answer 21

Okay, reading on from that page, they also say that it is = to 0 which signifies that H is only dependent on temp...

Answer 22

So I guess no correction is necessary when trying to correct for pressure!

Answer 23

haha that makes more sense.. dude I'm sorry but I'm studying for a test tmrw, if you still haven't figured out ill ask someone (i have thermo at 9 am) good luck

Answer 24

Thanks for the help so far! I have been able to get zero help from anything/anyone in the last week. I appreciate it! This class is seriously too much work for one stupid credit, I'm actually considering dropping it, lol!

Answer 25

The partial derivatives are useful for calculating total error propagation, is that a possibiity here?

Answer 26

Oh my.

Answer 27

I'm pretty sure we were going to need to propagate error as well as doing all of this crap. @abb0t "Oh my, you figured it out?" or "Oh my, this is all wrong?"