Question

What does the Constant R in the Ideal Gas Law mean?

Answer 1

Regnault constant, or Universal Gas Constant.

Explanation:

Gas constant, R, is named after the French chemist Henri Victor Regnault. It is also called the Universal Gas Constant.

Gas constant is equivalent to Boltzmann constant `k_B` multiplied by Avogadro's number `N_A = 6.0221413xx10^23` `"things"cdot"mol"^(-1)`, expressed in terms of energy.

There are many values of R depending on the units used.

Here are some examples:

`"8.314 J"cdot"K"^[-1]"mol"^[−1]`
`8.314xx10^7` `"erg"cdot"K"^[−1]"mol"^[−1]`
`8.314xx10^[−3]` `"amu" cdot["km"^2]/"s"^2"K"^[−1]`
`8.314` `"L"cdot"kPa"cdot"K"^[−1]"mol"^[−1]`
`8.314xx10^[−5]` `"m"^3 "bar"cdot"K"^[−1]"mol"^[−1]`
`8.314xx10^[−2]` `"L" "bar"cdot"K"^[−1] "mol"^[−1]"`
`62.36` `"L"cdot"Torr"cdot"K"^[−1]"mol"^[−1]`
`0.08206` `"L"cdot"atm"cdot"K"^[−1]"mol"^[−1]`

Answer 2

R can be viewed as a scaling factor for molar energy of ideal gas law. For ideal gas law, energy can be viewed as increasing linearly with temperature. `E=alphaT`

Explanation:

Through derivation. it was shown that for one-dimension, `E=1/2 RT` while for 3 dimension `E=3/2 RT`
The above is for 1 mole of ideal gas. For 1 molecule of gas, we know that `R=N_{A} k`
So 1 molecule of ideal gas moving in 3 dimension is `E=3/2 kT`
You can equate the kinetic energy of the molecule `E=1/2 m v^2` to previous equation and get
`E=3/2 kT= 1/2 m v^2`

Read more
http://homepage.smc.edu/gallogly_ethan/files/ideal%20gas%20law%20derivation.pdf

https://en.wikipedia.org/wiki/KT_(energy)