Gas Constant R

[lwon Dis2I]

Do we always use the gas constant R of 8.314 for nRT equations?

[Varsha Ravi 3E]

For problems where we want a result in J, we usually use 8.314. For PV = nRT, and other types of calculations where we don't need an answer in J, we usually use a different gas constant.

[Chem_Mod]

No, you want to be aware of the units.
R= 8.314 J/mol.K or R= 008206 L.atm/mol.K
Make sure you have the units of each calculation listed so you know which you need to use

[905290504]

I recommend always writing out your units in your equations to make it easier to identify which R to use

[Tikva Cohen 1K]

that's normally the case, but don't make that assumption because you don't wanna mess yourself up. always use whichever one cancels all the right units out.

[Samudrala_Vaishnavi 3A]

Yes, we usually use the gas constant so we can get our final value in moles. However, we use the 8.026 times 10^-2 value whenever we try to derive any values from the ideal gas equation since those values aren't in joules.

[JaesalSoma1E]

My trick for remembering is to use 8.314 when solving for energy or joules and using 0.08206 when solving for moles, volume, temperature, or pressure.

[Mary Shih 3J]

usually yes because that equation doesn't account for volume (0.082 value). Write out the units for the other numbers to check for unit cancellation when you are unsure.

[Jordan Tatang 3L]

No, you want to look at the units and make sure that the gas constant you are using applies to the corresponding units.

[Keeryth Sandhu 1H]

I recommend writing out the units and then picking which gas constant works best with those units

[AustinMcBrideDis3L]

General rule of thumb: use .08206 for when you are using PV=nRT, and use 8.314 for every other situation!

[Allan Nguyen 2G]

It really just depends what you want your answer to end in. 8.314 is typically used when you want your answer to end in joules.

[SophiaJenny3I]

Hi! Not necessarily. Always make sure you write out the units you have, and observe the unit you want and make sure everything else cancels out. This has helped me make sure I don't choose the wrong one! 8.314 is usually used when you want to end in J/kJ if you convert it.

[Kelly Tran 1J]

The R you would use depends on the units! Use R = 8.314 J/mol.K or R = 0.08206 L.atm/mol.K depending on the units of the other terms.

[austin-3b]

Depends on what you are trying to find. If joules, use 8.314, if not then you use 0.0821.

[LeanneBagood_2F]

i think the easiest way to know which value of R to use is to look at the units of the other values you are given in the question. based on that, you can determine which R value to use as your objective is to cancel things out so you are left with the correct units for your answer.

[Carly_Lipschitz_3H]

It really depends on what you want your end value to be in units. If you are trying to get joules, then use 8.314. Make sure the gas constant you are using works with the units you are given with and trying to find.

[Navdha Sharma 3J]

The value of R which has to be used depends on the units: 8.314 J mol^-1 K^-1 or 0.08206 L.atm mol^-1 K^-1
Also, you don't have to remember these, just look it up on the equation sheet!

[Leyla Anwar 3B]

The R's are actually the same just calculated with differnt units, typically you use R=0.0821 for PV=nRT but if you want J then you would use R=8.314. It's all about units.

[Kayla Booker 1F]

It depends on the units of the other variable, you want to use the R value that allows units to cancel out.

[Ivy Tan 1E]

Hi!
It depends on what the units are in your calculations, so sometimes you will use R=8.314 J/Kmol and sometimes you will use R=0.08206 Latm/Kmol. Usually if you're using the PV=nRT equation for an ideal gas calculation, you'll use 0.08206 Latm/Kmol because the units match up with the other units in the equation. Hope this helps!

[Olivia Smith 2E]

As everyone has said it all depends on units. If the problem is asking for energy then it will most likely be the 8.314 one you use as it includes joules. If the problem is not asking for energy then you will use the other two values depending on the units for pressure

[Arnav Saud 2C]

When working with the gas constant R, the most important thing you need to look at are the units that you have and the ones you need to find. For example, if you know the pressure, temperature, mass(in mols) and need to find the volume, you'll want to use the 8.206E-2 value.

[RitaThomas_3G]

Hey! So initially I was confused with this concept too, but then I found that it was easiest to see what units I needed for my final answer. Then, I used the R value which allowed me to get the desired result (by cancelling out units that I needed).

[Kyle Dizon 3A]

The only way I am surviving the calculations right now is referring to the units. Use the equation sheet to refer to the proper units to identify the correct steps to get the units needed.

[Lauren Mungo 1K]

No you have to use the R values that corresponds to the units given in the problem

[Colin Squire 3B]

The gas constant really depends on the units you need to cancel in order to find what you want. This can also mean changing the given value in J to kJ so that we a can minimize the amount of conversions done.

[Nicole Critzer 2L]

The gas constant you use depends on the units of the given information. So far it seems that most of the problems we've been given do use the 8.314 J/ (K*mol) so I wouldn't stress about it too much. However just make sure to know which constant to use should you be given something in units that differ from this R value.

[Alejandro Gonzalez 2G]

The gas constant you use depends on the units you have to convert to in the problem, whether they be L*atm, J, L*Torr, etc.

[Megan ODonnell 3F]

It depends on what units are given or what units the desired value is.

[Crystal Pan 2G]

It depends on what the problem is asking. You typically should look at the units to determine which gas constant R to use.

[Mansi Solanki 3A]

We use 8.314 for the nRT equations that involve work or entropy because we want the final result to be in Jules (J). However, when we just want to use the ideal gas law, we use 0.0821 because the units are atm*L/mol*K

[Hannah Lechtzin 1K]

We typically use 8.314 for equations involving energy change (Joules). For the ideal gas law we usually go for one of the other R constants, depending on which one best fits the units we are using.

[Queena Chu 3E]

Most of the time yes. But make sure to remember the units and make sure they end up canceling out.

[Nick Saeedi 1I]

8.314 is only used when the final answer you are trying to get is in joules.

[Jerry_T]

The gas constant used depends on the desired units for your final answer. If it includes joules, then 8.314 is suitable.

[Taha 2D]

it depends on the units you used to solve the question. the two options are R= 8.314 J/mol.K or R= 008206 L.atm/mol.K

[Charmaine Ng 2D]

it depends on the units you used to solve the question. the two options are R= 8.314 J/mol.K or R= 008206 L.atm/mol.K

I agree! Generally, we usually use 8.314, while 0.08206 is used for PV=nRT. That's just generally though, so it's always safer to check by units

[Aria Movassaghi 1A]

Not necessarily, it depends more on units. Eg: if joules are in the problem, it is probably going to be the 8.314 value for R.

[Joanna Huang]

It depends on the units, but usually yes, we use 8.314!

[Sam Wentzel 1F 14B]

No, use .08206

[Tiao Tan 3C]

I usually look at the units given in the problems to determine which R value to use. For example, if we want our answer to be in J, use 8.314.

[DPatel_2L]

Use the value with the same units in the problem.

[Moura Girgis 1F]

It ultimately depends on the units. 8.314 tends to be used for energy problems which deal with joules, while 0.08206 is used for problems with volume, moles, pressure, or temperature.