## atm vs. bar?

$PV=nRT$

Tyra Nguyen 4H
Posts: 74
Joined: Fri Sep 28, 2018 12:25 am

### atm vs. bar?

What's the difference between atm and bar when calculating the equilibrium constant with pressure?

Tarika Gujral 1K
Posts: 62
Joined: Fri Sep 28, 2018 12:27 am

### Re: atm vs. bar?

Different units of measurement
Thus entails use of different value for R constant.

Shally Li 2C
Posts: 30
Joined: Fri Sep 28, 2018 12:22 am

### Re: atm vs. bar?

Bar is the standard unit of pressure but 1 atm is equal to approximately 1.01 bar so when calculating equilibrium constant they are about the same.

Simran Rai 4E
Posts: 58
Joined: Fri Sep 28, 2018 12:17 am

### Re: atm vs. bar?

Regarding pressure, they're both just units measurements. But if you wanted to figure out concentration you would need to use atm.
For example, if you're given partial pressure but the units are in bar and you want to use PV=nRT to find concentration (with volume given), you'd need to convert to atm because those are the units used in the R constant and therefore those would allow you to cancel out.

vaishali 1D
Posts: 61
Joined: Fri Sep 28, 2018 12:19 am

### Re: atm vs. bar?

They're different units of measure for pressure. It's essential that you identify the correct units in order to plug in the correct value for the R constant in PV=nRT.

Eruchi Okpara 2E
Posts: 53
Joined: Fri Sep 28, 2018 12:28 am

### Re: atm vs. bar?

There is a difference in the conversion formula that is used for both. I think its a difference in the R constant that is used for the formula PV=nRT.

Alexandra Albers 1D
Posts: 61
Joined: Fri Sep 28, 2018 12:18 am

### Re: atm vs. bar?

atm and bar are both units of measurements for the partial pressures of gases. If you have a problem where you need to find the equilibrium constant in partial pressures then you can leave the gases in either atm or bar (whichever they are given in). The only time that the difference becomes relevant in the problem is if you need the gases in concentrations and not partial pressures because you will need to change the value of R (the gas constant) depending on which unit you are in.

Bruce Chen 2H
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Joined: Fri Sep 28, 2018 12:26 am

### Re: atm vs. bar?

I believe that in the calculations that we are doing, we should use the unit that they give us... otherwise, I think they are interchangeable.

Karina Jiayu Xu 4E
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Joined: Fri Sep 28, 2018 12:29 am

### Re: atm vs. bar?

On the test I used bar and it was fine

isarose0
Posts: 62
Joined: Fri Sep 28, 2018 12:15 am

### Re: atm vs. bar?

bar is slightly more accurate than atm, by one percent

shaunajava2e
Posts: 66
Joined: Fri Sep 28, 2018 12:26 am

### Re: atm vs. bar?

they are both units of measurement for pressure and depending on your TA, both should be fine to use

Millicent Navarro 1I
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Joined: Fri Sep 28, 2018 12:25 am

### Re: atm vs. bar?

Both atm and bar are units of partial pressures of gases! However, it's important you stick to just one or the other when calculating equilibrium constant with pressure.

Dayna Pham 1I
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Joined: Fri Sep 28, 2018 12:16 am
Been upvoted: 3 times

### Re: atm vs. bar?

Karina Jiayu Xu 4E wrote:On the test I used bar and it was fine

My TA said she would’ve accepted both atm and bar on the test, but I’ve also heard that atm is more standard.

Amar Singh
Posts: 31
Joined: Fri Sep 28, 2018 12:20 am

### Re: atm vs. bar?

Practically you can usually use both but you should definitely use whichever one is specified in the problem.

Edward Suarez 1I
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Joined: Fri Sep 28, 2018 12:27 am

### Re: atm vs. bar?

i had the same question but I realized that most of the problems that had bar in the question had the answer in bar too

Esther Lee 4H
Posts: 67
Joined: Fri Sep 28, 2018 12:29 am

### Re: atm vs. bar?

im not sure if there's like a rule for it but it seems like we've been using bar way more than atm. they're both measuring pressure so I dont think there's a specific one you need to use but someone correct me if I'm wrong please

Brian Kwak 1D
Posts: 88
Joined: Fri Sep 28, 2018 12:17 am

### Re: atm vs. bar?

I think the most important part for atm and bar is to be consistent with the units throughout the calculations so you don’t get points deducted. I would really pay attention to the wording of the problem if they give you atm then just use atm throughout your calculations. Consistency is important, that’s what I think also either atm or bar is acceptable from what I was told by my TA. The choice is really dependent on the information they give you and the units in the given information.

Anna O 2C
Posts: 98
Joined: Fri Sep 28, 2018 12:19 am

### Re: atm vs. bar?

They simply correspond with different values, but distinguishing between them is essential in order to use the correct R constant value.

Xingzheng Sun 2K
Posts: 62
Joined: Fri Sep 28, 2018 12:29 am

### Re: atm vs. bar?

So which one is the right unit for the equation PV=nRT?

Jeannine 1I
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Joined: Fri Sep 28, 2018 12:27 am

### Re: atm vs. bar?

Xingzheng Sun 2K wrote:So which one is the right unit for the equation PV=nRT?

I'd say it depends on which unit the problem uses. Can anyone confirm this?

Lauren Huang 1H
Posts: 60
Joined: Fri Sep 28, 2018 12:16 am

### Re: atm vs. bar?

The units can be atm or bar depending on the problem. Note that this will change the value of R.

Shibhon_Shepard
Posts: 62
Joined: Wed Nov 15, 2017 3:04 am

### Re: atm vs. bar?

when calculating for R just use the 8.314 value

Nghi Nguyen 2L
Posts: 61
Joined: Fri Sep 28, 2018 12:18 am

### Re: atm vs. bar?

there isn't that much of a difference between them , just use the unit that the problem states and make sure your R value corresponds

jocelyntzeng
Posts: 59
Joined: Fri Sep 28, 2018 12:18 am

### Re: atm vs. bar?

you can easily convert between the two but just be careful to use the right R value corresponding