## R constant for PV=nRT

Jessica Castellanos
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Joined: Sat Aug 24, 2019 12:17 am
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### R constant for PV=nRT

What is the the value of R in PV=nRT? I've seen two different values and don't know which is which.

Kevin Antony 2B
Posts: 99
Joined: Sat Sep 07, 2019 12:16 am

### Re: R constant for PV=nRT

R is equal to 8.3145 x 10^-2

sarahforman_Dis2I
Posts: 109
Joined: Sat Aug 17, 2019 12:18 am

### Re: R constant for PV=nRT

Jessica Castellanos wrote:What is the the value of R in PV=nRT? I've seen two different values and don't know which is which.

Yes, you are correct that there are two values for R. The difference between these values are the units that are used. This means that you need to be very careful when you are using the ideal gas law in order to make sure that you are using the correct units.
For example, R= 8.314 J/(Kmol) and .008206 L(atm)/(Kmol) and 0.008314 L(bar)/(Kmol) and 62 L(Torr)/(Kmol).

Use the gas constant that will cancel with the units that you were given in the problem. For example, if you were given pressure in atm, use .008206 L(atm)/(Kmol). If you were given a pressure in Pa (which you could easily convert to Bars) use 0.008314 L(bar)/(Kmol)

Amy Kumar 1I
Posts: 114
Joined: Thu Jul 11, 2019 12:15 am

### Re: R constant for PV=nRT

The R values are constant and change based on the units of pressure being used.

Kallista McCarty 1C
Posts: 212
Joined: Wed Sep 18, 2019 12:18 am

### Re: R constant for PV=nRT

The R value will be given on the constant and equations sheet on the test! I know that there are different units that you use depending on the question, but they will both be given

205405339
Posts: 77
Joined: Thu Jul 11, 2019 12:16 am

### Re: R constant for PV=nRT

R can have different values depending on what units are needed for the equation

Posts: 113
Joined: Thu Jul 11, 2019 12:16 am

### Re: R constant for PV=nRT

Look at the units of pressure to differentiate between the R constants. Whichever R constant contains the same units of pressure as the data you have is the one you should choose to make further calculations.

Eunice Nguyen 4I
Posts: 100
Joined: Sat Aug 17, 2019 12:17 am

### Re: R constant for PV=nRT

R value is a constant and is chosen based on which unit is given in the problem. Make sure to keep an eye out for the unit so that you know which R value to use!