\(r\,\, = \,\,\, \frac{R}{{{M_w}}}\,\, = \,\,\,\frac{{PV}}{{T\,\, \times \,\,{M_w}}}\,\, = \,\,\,\frac{{76\,\, \times \,\,13.6\,\, \times \,\,981\,\, \times \,\,22400}}{{273\,\, \times \,\,4}}\,\, = \,\,2.08\,\,\, \times \,\,{10^7}\,\,erg\,\,{g^{ - 1}}\,\,{K^{ - 1}}\)

\({c_p} - {c_v} = \,\,\,\frac{r}{J}\,\, = \,\,\frac{{2.08\,\, \times \,\,{{10}^7}}}{{4.186\,\,\, \times \,\,{{10}^7}}}\,\,\, = \,\,0.5\,\,\,cal\,\,{g^{ - 1}}\,\,{K^{ - 1}}\)