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What does R stand for?

Posted: Tue Jan 16, 2018 2:28 pm
by Mike Matthews 1D
The equation relating the heat capacity of an ideal gas at constant pressure and the heat capacity of an ideal gas at constant volume is:
Cpm=Cvm + R
That being said, what is R? Is it the gas constant? If so how does one go about deciding which value to use for R?

Re: What does R stand for?

Posted: Tue Jan 16, 2018 2:59 pm
by Kailey Brodeur 1J
R is the ideal gas constant. You decide what value of R you should used based upon what units you are using.

Re: What does R stand for?

Posted: Tue Jan 16, 2018 4:58 pm
by Jessica Nunez 1I
As mentioned, R is the gas constant which is equal to . . .
8.314 J.K^-1.mol^-1 = 8.206 x 10^-2 L.atm.K^-1.mol^-1 = 8.314 x 10^-2 L.bar.K^-1.mol^-1 = 62.364 L.Torr.K^-1.mol^-

Re: What does R stand for?

Posted: Tue Jan 16, 2018 8:34 pm
by Nicole Jacobs 1C
R should also be given on the formula and constant sheet Lavelle gives us for the test

Re: What does R stand for?

Posted: Tue Jan 16, 2018 8:53 pm
by Sarah Rutzick 1L
Going off of what everyone else said, there are several different gas constants so its important to use the one that ensures the correct units cancel out.

Re: What does R stand for?

Posted: Tue Jan 16, 2018 11:19 pm
by Adrian Lim 1G
Just to clarify, R is the ideal gas constant and its units are given per mole. Thus, when you are using this for q = mcdeltat, make sure the m is amount given in moles so the moles with the c would cancel.

Re: What does R stand for?

Posted: Thu Jan 18, 2018 3:25 pm
by Alejandra Rios 1L
R is a constant which is used in ideal gas calculations. There are several values which you can use for R depending on what unit of pressure you are working with. These values will be given!

Re: What does R stand for?

Posted: Sat Jan 20, 2018 2:56 am
by Juanyi Tan 2K
The one that we most commonly use in thermochemistry is R = 8.314 J·K-1·mol-1

Re: What does R stand for?

Posted: Sat Jan 20, 2018 10:54 am
by Justin Folk 3I
Heat constant. When do you use 8.314 and when do you use 0.00821?

Re: What does R stand for?

Posted: Sat Jan 20, 2018 12:06 pm
by Cassandra Mullen 1E
Justin Folk 3I wrote:Heat constant. When do you use 8.314 and when do you use 0.00821?


Looking at the units helps you to determine which R to use. If you're using the ideal gas equation and pressure is in atm and volume is in L, then you would use 0.00821 Latm/molK. Homework problem 8.49 is an example of using the other R value, 8.314 J/Kmol.

Re: What does R stand for?

Posted: Fri Feb 16, 2018 5:16 pm
by Justin Folk 3I
Yes, you're right sorry. THere's multiple R. You need to look at the units, on the third row of equation sheet. THanks

Re: What does R stand for?

Posted: Sun Feb 18, 2018 8:51 pm
by Jaewoo Jo 2L
I think until now, we've mostly seen the R values with atm or joules, and like what everyone said above, you just use the value with the units that cancel with corresponding units in your calculations.

Re: What does R stand for?

Posted: Mon Mar 12, 2018 9:56 am
by Annie Lieu-1H
The ideal gas constant! Like everyone said, make sure to look at the equations sheet and look at the right units to use for numbers in a particular problem.

Re: What does R stand for?

Posted: Thu Mar 15, 2018 7:44 pm
by Warda Sahib 2J
R is the ideal gas constant.