Consider a buffer composed of the weak acid ha and its conjugate base a−. part a which pair of concentrations results in the most effective buffer? which pair of concentrations results in the most effective buffer? 0.90 m ha; 0.10 m a− 0.50 m ha; 0.50 m a− 0.10 m ha; 0.90 m a− 0.10 m ha; 0.10 m a−