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Looking for the value of the Molar Gas constant. I am unsure because NIST has

8.314 462 618 J/(mol*K) 

while Wikipedia says

8.314 462 618 153 24 J/(mol*K).

Not clear to me if either is before or after the 2019 redefinition. Wikipedia has a template saying it "might" be before, but NIST is says it came from "2018 CODATA recommended values".

I am going to be interested in other constants too.

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As per the 2019 redefinition of the SI base units, the molar gas constant is exactly

$8.314\,462\,618\,153\,24\,J\,kg^{-1}\,mol^{-1}$

The wikipedia number comes from the full multiplication of the Boltzmann constant, $k_B$, and the Avogadro constant, $N_A$, both numbers defined as having no uncertainty due to the aforementioned recent changes to the SI. I don't know why your link hasn't updated their website but you can click the actual symbol of the molar gas constant on the website you linked to check that it is, indeed, derived from the two other constants I mentioned.

You can then use a full precision calculator to verify the number yourself. Note that Google's calculator does not show you the full decimal value, but other online calculators will. For most calculations, however, these last few digits aren't going to affect anything much at all. Other constants similarly can be found on the Wikipedia page I linked above.

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You're missing two important details from the NIST website: i) there are three dots after the value, that is, not $8.314 462 618\,\mathrm{J/(mol\,K)}$ but $8.314 462 618...\,\mathrm{J/(mol\,K)}$; ii) the word "exact" in the uncertainty field.

The molar gas constant $R$ is the product of the Avogadro constant $N_\mathrm{A} = 6.022\,140\,76\times 10^{23}\,\mathrm{mol}^{-1}$ and the Boltzmann constant $k = 1.380\,649\times 10^{-23}\,\mathrm{J\,K}^{-1}$ which, in the revised SI, are defining constants with the given exact values. The values reported by both NIST and Wikipedia have been calculated according to the equation $R=kN_\mathrm{A}$, with the values of $k$ and $N_\mathrm{A}$ according to the revised SI, but the value reported by NIST has fewer digits.

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