Question

What does the R stand for in the ideal gas law (PV=nRT)?

Answer 1

The units of the universal gas constant `R` is derived from equation `PV = nRT`. It stands for Regnault.

If

• the pressure `P` is in atmospheres (atm),
• the volume `V` is in liters (L),
• the moles `n` is in moles (mol),
• and temperature `T` is in Kelvin (K),

then `R` is in `"L"cdot"atm/mol"cdot"K"`. `R` has the value `"0.082057 L"cdot"atm/mol"cdot"K"` with the above units for the remaining variables.

In other scenarios with pressures of `"bars"` instead, you may also use `"0.083145 L"cdot"bar/mol"cdot"K"`. However, temperature must always be in Kelvin (K), as `R` uses units of `"K"`.

There is a variation of the ideal gas law that uses the density of the gas with the equation

`PM = DRT`

where `M` is the molar mass in `"g/mol"` and `D` is the density of the gas in `"g/L"`.

Lastly, this video may help introduce you to the ideal gas law.

I hope this is helpful.