gas constant R
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Re: gas constant R
I believe units must be given for pressure because otherwise how would you choose R? Since pressure can be expressed in: atm, bar, pa, tor, etc. units have to be given to properly use PV=nRT to convert to molarity.
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Re: gas constant R
The units of pressure would need to be given. If pressure is in atm, then use R = 0.08206 L*atm/K*mol to cancel out. If pressure is in bar, the unit for R would be L*bar/K*mol, and for torr it is L*torr/K*mol.
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Re: gas constant R
There have been a couple of questions that do not specify the units for pressure. I believe that you can use whichever value for R that is easiest for you, just make sure you are clear that your final answer or numbers chosen corresponds directly to the value of R that you used.
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Re: gas constant R
Yes, it depends on the units.
There are 4 values that are used more often:
R = 0.0821 L·atm/(mol·K) = 8.3145 J/(mol·K) = 8.2057 m3·atm/(mol·K) = 62.3637 L·Torr/(mol·K)
There are 4 values that are used more often:
R = 0.0821 L·atm/(mol·K) = 8.3145 J/(mol·K) = 8.2057 m3·atm/(mol·K) = 62.3637 L·Torr/(mol·K)
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Re: gas constant R
To determine which gas constant to use, you would refer back to the question and find the units that they are using. For example, If the pressure is in atm, then you can use R = 0.08206 L*atm/K*mol. However, if the pressure is in bar, you can use R = L*bar/K*mol and so on.
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Re: gas constant R
It will matter since not all the values are the same. If the pressure units aren't specified, you should look at all the other units in the problem so you can see which value is best for canceling the rest of them out.
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Re: gas constant R
It is important to know the differing units for the gas constant R because it can differ depending on what the question is asking for.
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Re: gas constant R
make sure you keep in mind what units are in the question and use the correct value in the context :)
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Re: gas constant R
As long as the units cancel, and you convert to whatever the answer is looking for, it should always work!
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Re: gas constant R
The units of pressure will most likely be given and you want to make sure you are using the right units throughout while you solve a problem. Hope this helps!
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Re: gas constant R
Using the right unit that is given in the question and solving it throughout would be useful.
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Re: gas constant R
Usually the units are specified but if they're not specified as long as the units cancel out you should be able to use whichever you like.
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Re: gas constant R
As long as the units cancel and you end up with the correct unites you are looking for, then it does not matter.
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Re: gas constant R
Depending on the units given in the problem and equation that you are using, the R constant will change. Usually, you can tell from the problem.
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Re: gas constant R
It is important to know what units are given to you in the question to see what value you have to use, but as long as your units cancel out and you have the correct units at the end then you should be fine.
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Re: gas constant R
There are several units that represent R, I say it's best to look at the units and see which one would be the most ideal to use. For example we have: 8.314 J*K^-1*mol^-1, 8.206*10^-2 L*atm*K^-1, and 8.314 *10^-2 L*bar*K^-1*mol^-1
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