Gas Constant

[505673236]

What gas constant(R) are we supposed to use there are multiple on the formula sheet when using the ideal gas law?

[Chem_Mod]

It depends on what equation you are using the gas constant for/what units you are using. Make sure all of your units match every time you use the gas constant.

[Miracle Ogbonnaya 3B]

It depends on what the question is asking for as well.

[Arambula 1H]

Depends on the units provided and what they want the answer in. You may have to convert between them.

[Oscar Tan 1L]

The gas constant R depends on what units are being used!

[chloeremigio1e]

Like the other answers, the gas constant R that you use will just depend on what the question asks for! Personally, I got a little confused a couple times too, but just be sure to double check that your units are consistent with what the problem is using :)

[Min Hur 1L]

It completely depends on the problem, but if you just double check the units for the equations given, you should be golden!

[Sydney Min 2H]

Although there are multiple versions of the R constant depending on the unit, our equation sheet gives us 3 versions each with different units. Just make sure that the units match with the units given in the question and they cancel out. I like to write down the units when solving so that I can ensure that the units cancel out evenly.

[Ken Kwok 2J]

It depends on the units but in J/(mol*K), R is 8.314.

[Mariet Garcia 1E]

I believe it depends on each problem! You just need to check the units to make sure you are using the one with the correct units.

[Ojas Sharma 2G]

The value you use for r is dependent on what you are given in the problem. The equation sheet has multiple values listed so just make sure your units match and that should be fine.

[Emily La 2B]

Yea, usually the gas constant is R = 8.3145 J/K·mol or R= 0.08206 L·atm/K·mol. It depends on the problem and its units that are given.

[Caitlin_Chheda_1K]

Hi! It depends on the question and the units in the question. However, I've only really used 0.082 or 8.314 in this class, and for 14B I tend to use 8.314 for the problems more than 0.082. I hope this helps!

[Wesley J the BioChem Kid]

For thermodynamics you usually use 8.314J/Kmol because you're dealing with energy transfers. However for ideal gas situations it is most often 0.08206Latm/Kmol but this value is also altered to fit the correct pressure units (ex. 62.363LmmHg/Kmol).

[Ilisa Risal 1H]

The gas constant used depends on what equation is being used. A trick for figuring out which one to use is looking at the units in your equation and making sure they cancel out.

[Kaylee Cheng 3E]

The R value is dependent on the units provided in the situation presented.

[Kaylee Cheng 3E]

The R value is dependent on the units provided in the situation presented.

[Brandon_G_1H]

Hello! The R value, 0.08206, is going to be used in the equation PV=nRT. While, the R value 8.314 will be used when the question is asking for work, Gibbs free energy, or entropy, etc.

[Rebecca_Park_1G]

The gas constant depends on the units being used in the specific problem. For example, if we have pressure in atm and volume given in liters, then we would use 8.206 x 10^-2. However, if we need to cancel out J and K, such as in problems involving work and free energy, we would use R=8.314.

[marika roberts 3l]

Hi! To answer your question, the gas constant you use is dependent on the units of the other components of the formula. When I am not sure which to use, I will write my chosen equation out and list the units I will be using for each element. Pay special attention to the units of what you are trying to find. Then look at what will already cancel out. I will then compare these units with the units I want to end up with and consult the formula sheet to see which R will best fill in the gaps to get me to my desired units! Another tip is equations of the same type/topic will often consistently use the same R value so take a look at textbook questions or examples from lectures to see which R is used when R

[205898077]

The constant R is dependent on which units are being used in the problems.

[nataliemartin2H]

The other replies are correct in that it depends on the units. However, if you are stuck during the exam and blanking on which to use, it might not help at the moment to try and think about the units. If this happens and you have to guess, use 0.08206 in PV=nRT and 8.314 in anything else. This method won't work 100% of the time but it is a good backup plan that will often get you the right answer. Good luck!

[Jenifer_Fonseca]

Hello,
It really depends on what units we are given in the problem.
I will list the units and their respective R constant below:

L-atm-/mol-K. 0.08206
J/mol-K. 8.314
cal/mol-K. 1.987
m^3-Pa/mol-K*
L-torr/mol-K 62.36

Hope this helps!