code: def ideal_gas(target, pressure='pore.pressure',
                temperature='pore.temperature'):
      r
      R = 8.31447
      P = target[pressure]
      T = target[temperature]
      value = P/(R*T)
      return value
docs: r"""
      Uses ideal gas law to calculate the molar density of an ideal gas
  
      Parameters
      ----------
      target : OpenPNM Object
          The object for which these values are being calculated.  This
          controls the length of the calculated array, and also provides
          access to other necessary thermofluid properties.
  
      temperature : string
          The dictionary key containing the density in kg/m3
  
      pressure : string
          The dictionary key containing the pressure values in Pascals (Pa)
  
      Returns
      -------
      rho, the density in [mol/m3]
  
      Notes
      -----
      This method uses the SI value for the ideal gas constant, hence the need to
      provide the temperature and pressure in SI.  In general, OpenPNM use SI
      throughout for consistency.