value of R


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connie ma 3G
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value of R

Postby connie ma 3G » Sat Jan 09, 2021 2:19 pm

in the ideal gas law PV=nRT i know that R can take on different values. but how do you know which value to use? theres 4 different R values on our equation sheet and im not sure when you would use each one.

Varsha Ravi 3E
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Re: value of R

Postby Varsha Ravi 3E » Sat Jan 09, 2021 2:40 pm

It depends on the units of the quantities in the problem. For example, one of the R values on the equation sheet uses Torr, while others use atm and bar, which are other units for pressure.

Sean Wang 1F
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Re: value of R

Postby Sean Wang 1F » Sat Jan 09, 2021 2:53 pm

Like Varsha said, the value of R depends on the units given. If you're in doubt I believe that in this class, we are most commonly given atms which mean you use 8.206 x 10^-2 for R.

Dominic Benna 2E
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Re: value of R

Postby Dominic Benna 2E » Sat Jan 09, 2021 2:56 pm

It basically depends of the units in the equation. However, I think Lavelle said that we would be using atm mostly, so the most likely value you would be using for R would be 8.206 x 10^-2.

Sophia Kalanski 1A
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Re: value of R

Postby Sophia Kalanski 1A » Sat Jan 09, 2021 5:23 pm

it depends on the units given! Each R value uses different kinds of units so be extra sure to use the right R value and to pay close attention to the units given in the problem

keely_bales_1f
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Re: value of R

Postby keely_bales_1f » Sat Jan 09, 2021 5:51 pm

To know which value of R to use, make sure you read the problem that you are doing carefully. It should give you context clues as to whether you are dealing with atms, bars, etc. Then you would use the R value for the specific unit.

darchen3G
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Re: value of R

Postby darchen3G » Sat Jan 09, 2021 6:14 pm

As the others said, it depends on the units in the problem. Here is a handy chart:
Image

Sandra Kim 2B
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Re: value of R

Postby Sandra Kim 2B » Sat Jan 09, 2021 6:40 pm

if you're worried that different units will be on the test for constant R, don't worry! on the constants and equations sheet that we are allowed to use during tests, Dr. Lavelle put the value of R for many different units! you can find the sheet on the 14b website :)

Mari Williams 1K
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Re: value of R

Postby Mari Williams 1K » Sun Jan 10, 2021 1:49 pm

From what I could tell, atm is most common in this course, so we'll probably use that value

Jerry_T
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Re: value of R

Postby Jerry_T » Sun Jan 10, 2021 2:16 pm

The value of R will be provided on the constants and equations sheet. In lecture, Lavelle stated we will be using atm primarily so I would use the R value of 8.206 x 10^-2.

Edwin Liang 1I
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Re: value of R

Postby Edwin Liang 1I » Sun Jan 10, 2021 2:48 pm

Each value of R is different because different units are used. Use the value of R that corresponds to your problem.

LeanneBagood_2F
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Re: value of R

Postby LeanneBagood_2F » Sun Jan 10, 2021 3:52 pm

what exactly does R represent?
im a bit confused since it can be equal to different values depending on the units

Jaden Joodi 3J
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Re: value of R

Postby Jaden Joodi 3J » Sun Jan 10, 2021 4:35 pm

You use the value of R that would cancel out the units of the pressure, volume, and temperature.

Brian_Wu_3B
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Re: value of R

Postby Brian_Wu_3B » Sun Jan 10, 2021 4:55 pm

You use the value of R that cancels out the other units.

Abhinav Behl 3G
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Re: value of R

Postby Abhinav Behl 3G » Sun Jan 10, 2021 5:48 pm

In order to figure out which correct R value to use, you would simply look at the units given within the question. Technically, you can use any R value as long as you convert the given units in the question to match the units on the R value that you choose, but there's no reason to go through all that extra work when we are already given different R values on the constants sheet that correspond to the appropriate units.

Linette Choi 3L
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Re: value of R

Postby Linette Choi 3L » Sun Jan 10, 2021 8:27 pm

You can determine which value of R to use based on the units of the other values that you need to cancel out.

Keshav Patel 14B 2B
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Re: value of R

Postby Keshav Patel 14B 2B » Sun Jan 10, 2021 8:34 pm

R is just the constant so you only use different R values dependent on the values that are in front of you. So if you have atm as one of the pressures you will use the R value with atm.

t_rasul2I
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Re: value of R

Postby t_rasul2I » Sun Jan 10, 2021 8:57 pm

Like the comments said before, you will most likely use the standard R constant 8.206 x 10^-2. However if you have the other variables to solve for R or have different units, you would reevaluate how you find R. I don't think we have to worry too much about R in general.

Jack Kettering 3D
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Re: value of R

Postby Jack Kettering 3D » Sun Jan 10, 2021 9:02 pm

The value you use for R is dependent on the unit of pressure you are using but I believe R will always be provided to us.

Chinmayi Mutyala 3H
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Re: value of R

Postby Chinmayi Mutyala 3H » Sun Jan 10, 2021 10:47 pm

You look at the units of R. It depends on what units of pressure you're using.

Alejandro Gonzalez 2G
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Re: value of R

Postby Alejandro Gonzalez 2G » Sun Jan 10, 2021 10:57 pm

I believe the value of R depends on which units are used in the problem.

Gustavo_Chavez_1K
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Re: value of R

Postby Gustavo_Chavez_1K » Sun Jan 10, 2021 11:00 pm

It all just depends on the units that we are using. Each different value of R is essentially the same, they are only different because they are given in different units.

Brandon McClelland3L
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Re: value of R

Postby Brandon McClelland3L » Sun Jan 10, 2021 11:03 pm

The value for R is dependent on the units used. Normally people use most of the different ones we use are for different units of pressure like atm, bar, etc.

Jared Limqueco 3E
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Re: value of R

Postby Jared Limqueco 3E » Sun Jan 10, 2021 11:09 pm

R depends on the units used.

Emily_Stenzler_2H
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Re: value of R

Postby Emily_Stenzler_2H » Sun Jan 10, 2021 11:10 pm

I believe he said we are mainly using atm in this class, so I would convert to this unit (using the R for atm) if you are unsure! Just make sure all units match.


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