Units for Pressure

[Emma Edmond 3E]

When calculating for pressure, or using pressure in the ideal gas equation, should we always convert to pascals or can be leave it in the form of bar or atm?

[Sara Kashani 4j]

For idea gas law, the unit of pressure must be in atm.

[zhajee]

This cancels out the atm unit in R, which is .0821 L * atm/mol *K

[Claire Malley 2B]

You can use either bar or atm, pascals are not preferred because they do not have a gas constant like atm or bar, which are .08206 L.atm.K(-1).mol(-1) and .08314 L.bar.K(-1).mol(-1), respectively.

[Victor Qiu 1C]

I don't think the unit of pressure should must be in atm. I think just using same units in calculation would be fine.
R=8.314 J mol^-1 K^-1=0.08205 L atm mol^-1 K^-1=62.363 mmHg L mol^-1 K^-1

[Kathy_Li_1H]

Hi! I believe because the Standard unit for pressure is atm, we usually have to leave most answers units of atm.

[Kyla Roche 2K]

I recall hearing that 1 bar and 1 atm are essentially the same, therefore they are interchangeable, but that we will use atm.

[Gabe_Ek 1G]

Is there any case where we won't use atm? Such as having to change the final answer into Pa (Pascal) or kPa?

[Austin Aldujaili 2D]

I wouldn't think that there would be any situation where we need to convert to Pascals since Lavelle didn't talk about that unit at all. I think its important to just read the question and figure out what units they want their final answer in.

[Brian Nguyen 2I]

Don't convert to pascals. We use atm or barr in these problems involving pressure, so there is no need for conversion.

[Maddie Turk Disc 2J]

So do we ever need to convert to pascals or will it always be in atm.

[Andy Hernandez]

the unit of pressure should be in atm

[Kelly Ha 1K]

So do we ever need to convert to pascals or will it always be in atm.

I don't think we will have to convert to pascals since Dr. Lavelle hasn't mentioned it yet. We will most likely be given atm or bar units for pressure.

[josephspindler2H]

We will be using atm. As Dr. Lavelle stated in lecture, 1 bar is very close to 1 atm, so for our purposes we can just use atm.

[Adrienne Chan 1G]

We usually use atm for units as it is part of the SI system. Bar is not, and so we usually convert bar to atm unless the problem asks us to use bar specifically.

[AndrewNguyen_2H]

The constant uses atm so use atm to make sure the units cancel nicely.

[Shivani Kapur 2J]

I believe we will mostly be using atm for the extent of this class.

[Naomi Hernandez-Ramirez 1J]

like most I agree that the standard unit for pressure = atm, I know you've been getting Atm and bar, but I think atm is the correct unit

[Linette Choi 3L]

Along with everyone else I believe it should be in atm, however, it could vary on what units the question asks you to convert to.

[Keshav Patel 14B 2B]

Professor Lavelle said to use the atm for pressure. He said that it’s not too different and he prefers atm since it’s been around longer.

[Queena Chu 3E]

Hi! The unit should be atm.

[Melanie Lin 3E]

I usually convert to atm because of the given R constant (that uses atm). Since it will probably be given on the constants sheet, it'll be helpful converting to atm.

[Diana Aguilar 3H]

Hi! I believe the unit should be atm, I do not think we have to convert to pascals.

[nayha a 1E]

Hi! I believe we will be using atm (:

[Jose Miguel Conste 3H]

I believe it is with respect to the problem and what units they give, sometimes it can give mmHg or atm or torr, but take it with a grain of salt, you should ask a TA this question

[LarisaAssadourian2K]

Hello! I agree with the previous posts. We need to use atm so the units cancel out properly.

[Lily Mohtashami]

I agree, I think because Lavelle has only used atm we should be using atm as the units for pressure unless we learn otherwise.

[Joshua_Chan_3K]

Its probably best to leave it in ATM right now or for possibly the entire class but really each one of them has its own R value in the ideal gas law which you can search up or calculate just using the conversion factor (Although that method kinda takes away the whole point of leaving it in another unit). Just make sure not to use the wrong unit with the wrong R value and convert at the end to the unit the question is asking for.

[Anthony_Sandoval_1D]

It is in my opinion that we will be using atm in this specific class.

[Brandon Le 3C]

Generally, atm is the most commonly used unit when it comes to these kinds of problems. But there are different values of R in the ideal gas equation that would accommodate for different units of pressure.

[Rayna Irving 2C]

I'm pretty sure we use atm because its units line up with the R value we are given on the equation sheet so the units can cancel, but in the lecture he said that 1 atm is also pretty close to 1 bar if you're wondering.

[Muskaan Abdul-Sattar]

I believe units of pressure should be in atm.

[Teti Omilana 1G]

Units were left in atm based off of Lavelle's examples.

[Sam Wentzel 1F 14B]

Convert to ATM, so that the units cancel when plugging into the equation. Hope this helps!

[Caelin Brenninkmeijer 1G]

Pressure units should be in atm!

[Ariel Guan 1H]

i think pressure should be in atm

[Keeryth Sandhu 1H]

I believe for ideal gas law it should be in atm

[emwoodc]

Dr. Lavelle said that bar is technically the correct unit but since atm is so close to bar you can use atm!

[Sable Summerfield]

What is the difference between Barr and Atm? Why are they interchangeable?

[Susan Chamling 1F]

I think from examples in lecture atm tends to be used more often

[Karen Zheng_2K]

From Andrew's discussion section he said that we can use either bars or atm, but if something is in Pascals, you would need to convert it back to atm usually!

[Megan Sparrow 1A]

Okay, thank you for letting us know! Does anyone know if for the test if we are expected to know how to convert from Barr to atm or atm to pascals? I'm not sure if it was mentioned in the section outline or if this was just for practice on the homework and such.