code: def alpha0_carbonate(pH):
      
      alpha0_carbonate = 1/(1+(K1_carbonate/invpH(pH)) *
                              (1+(K2_carbonate/invpH(pH))))
      return alpha0_carbonate
docs: Calculate the fraction of total carbonates in carbonic acid form (H2CO3)
  
      :param pH: pH of the system
      :type pH: float
  
      :return: Fraction of carbonates in carbonic acid form (H2CO3)
      :rtype: float
  
      :Examples:
  
      >>> from aguaclara.research.environmental_processes_analysis import alpha0_carbonate
      >>> round(alpha0_carbonate(10), 7)
      <Quantity(0.00015, 'dimensionless')>