From the gas equation, pV = nRT, R =pV/nT . If p is measured in Pascal, V/n i.e., molar volume per mole in ${{m}^{3}}$ and T in kelvin, units of R are Pa ${{m}^{2}}$ ${{K}^{-1}}$${{mol}^{-1}}$ or J ${{K}^{-1}}$${{mol}^{-1}}$. As joule is the unit of work, R is the work done per mole per kelvin.