Which R to use?

[Kloey Reyes]

With the different values for R available for the PV=nRT equation, how do we know which one to use for different problems?

[Ethan_Choi_2I]

I think that it is based off the units in the problem? Like the units of the other variables and what units the question wants can influence what value of R you use.

[305607822]

Yeah I would use the R value with units that correspond to units used in the problem. Not 100% sure though, ask your TA.

[Baffour Adusei 1L]

Hi! It should largely depend on what units you are dealing with, like atm, torr, etc.

[105778693]

You should use the R that correspond to the units in the question. I found myself using R = 8.314 x 10^-2 L.bar.K^-1.mol^-1 when going through the achieve textbook questions though.

[Symphony Jackson 3K]

The R that you use is relative to the units used in the problem, so its not constant but changes depending on the question :)

[Jessica Berejikian]

For the equation PV=nRT, R is the gas constant: 8.314 J/(mol)(K). If the given units in the problem are not in SI units, the value may vary.

[Arshaun Faraji 2H]

I would use the R value with units that match those in the problem you are solving.

[Angela Harrington 2L]

I'm pretty sure which R-value you use just depends on the units.

[Carlie_Dorostkar_1A]

Does anyone know in what cases you would use the R constant of 8.314 J*K^-1*mol^-1? For the other 2 constants the units that measure partial pressure are included (atm and bar). Can joules be used to measure pressure?

[905565862]

You can choose which R value to use based off of the units used in the problem!

[Crystal Ma 2J]

Each value has different units, so I'd use the value that corresponds with the units of the problem given!

[Nicole Friday 1E]

The R you have to use depends on the units that the question is based on.

[405479701]

The units in the specific problem will tell you.

[Riya Sawhney 1C]

Look at the units you are using in the formula, and pick the R constant with the correct units. Remember, in the end you want all your units to cancel out.

[isabella garcia - 1G]

I was confused about this too, but apparently you use whatever units you were given in the problem.

[gracebinder3I]

Hi!
With the different units used in the Ideal Gas Law, the value of R depends on the question.
The most common value for R = 8.314 J/Kmol but 8.206E-2 Latm/Kmol and 62.364 LTorr/Kmol are also used.
I hope this helps!

[Mekenna Faulkner]

The R used is dependent on units. The values are the same with respect to their units. 8.314 is the most commonly used one since it’s units are J/kmol

[Jieun 2C]

Depending on the units of your values, a different numerical value of R should be used. R= 8.314 J/mol*K is most common.

[305561744]

Does anyone have a sheet that lists the different Rs with their units?

[Carlie_Dorostkar_1A]

Does anyone have a sheet that lists the different Rs with their units?

The sheet is called Constants and Equations and is on the Chem 14B section of lavelle's website.

[Cory Poon 3G]

Use the correct R by checking the units of the numbers in the problem.

[Jessica Sun 2I]

Depending on what units you are given for a specific problem, the R value will be different.

[Lindsey Walter 3E]

The value for R that you choose is dependent on the units given for the problem!

[Guadalupe_3B]

The R you should use depends on the units used in the problem.

[Vashe Sundar 3H]

The R value that you end up using depends on the units used in the problem, but once you get in the habit of doing problems, you kind of figure out which R to use when because of the typical units of that problem.

[Hayden Jackson]

Choosing which R to use depends completely on the units in the equation. For pv=nRT we always use R=.08206 atm x L / m x K because of how its units fit into the equation. Hope this helps!

[Nathan Morgan 2C]

The R you use will depend on the units given to you. For example if pressure was given in pascals you would use the 8.31 R constant so that pascals can cancel.

[Divya Mehta 2K]

You need to check the units of the numbers in the problem.

[bernal_maria1A]

Hi! I agree with everyone else, I think a visual would help. I refer to this chart, taking into account the rest of units of measurements.

[205819952]

Based on the units used in the problem, you can pick which R value to use.

[Aneesha_Nema_3C]

Hey! You would use the different values of R corresponding to the units of the other values in the expression

[Katherine Li 1A]

For all the equations using energy, use 8.314. The only equation that uses R = 0.08 that I can immediately think of is PV = nRT. Just, when in doubt, check the units of the problem.