## What does R stand for?

Mike Matthews 1D
Posts: 59
Joined: Fri Sep 29, 2017 7:04 am

### What does R stand for?

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?

Kailey Brodeur 1J
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Joined: Thu Jul 27, 2017 3:00 am

### Re: What does R stand for?

R is the ideal gas constant. You decide what value of R you should used based upon what units you are using.

Jessica Nunez 1I
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Joined: Thu Jul 13, 2017 3:00 am

### Re: What does R stand for?

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^-

Nicole Jacobs 1C
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Joined: Thu Jul 13, 2017 3:00 am

### Re: What does R stand for?

R should also be given on the formula and constant sheet Lavelle gives us for the test

Sarah Rutzick 1L
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Joined: Tue Oct 10, 2017 7:13 am

### Re: What does R stand for?

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.

Posts: 88
Joined: Fri Sep 29, 2017 7:03 am

### Re: What does R stand for?

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.

Alejandra Rios 1L
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### Re: What does R stand for?

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!

Juanyi Tan 2K
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Joined: Fri Sep 29, 2017 7:05 am

### Re: What does R stand for?

The one that we most commonly use in thermochemistry is R = 8.314 J·K-1·mol-1

Justin Folk 3I
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Joined: Wed Sep 21, 2016 2:56 pm

### Re: What does R stand for?

Heat constant. When do you use 8.314 and when do you use 0.00821?

Cassandra Mullen 1E
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### Re: What does R stand for?

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.

Justin Folk 3I
Posts: 43
Joined: Wed Sep 21, 2016 2:56 pm

### Re: What does R stand for?

Yes, you're right sorry. THere's multiple R. You need to look at the units, on the third row of equation sheet. THanks

Jaewoo Jo 2L
Posts: 31
Joined: Fri Sep 29, 2017 7:06 am

### Re: What does R stand for?

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.

Annie Lieu-1H
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### Re: What does R stand for?

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.

Warda Sahib 2J
Posts: 29
Joined: Thu Jul 13, 2017 3:00 am

### Re: What does R stand for?

R is the ideal gas constant.