Olutions that contain a weak acid, ha, and its conjugate base, a−, are called buffer solutions because they resist drastic changes in ph. when a solution contains a weak acid and its conjugate base or a weak base and its conjugate acid, it will be a buffer solution. for buffers containing a weak acid, the principal reaction is ha(aq)+h2o(l)⇌h3o+(aq)+a−(aq) unbuffered, a weak acid would ionize and the net reaction would proceed forward to reach equilibrium. however, when a significant amount of conjugate base is already present, the extent of the net reaction forward is diminished. thus, equilibrium concentrations of ha and a− are approximately equal to their initial concentrations. visualizing buffers you can visualize a buffer solution containing approximately equal concentrations of ha and a− in action using the following equation, where ka is the equilibrium constant: ka[h3o+]==[h3o+][a−][ha]ka[ha][a−] when the concentrations of ha and a− are relatively large, the addition of a small amount of acid or base changes their concentration negligibly. the result is that the ratio [ha]/[a−] maintains a value approximately equal to 1, and the [h3o+] is approximately equal to the ka value under buffer conditions. part a calculate the ph of the solution made by adding 0.50 mol of hobr and 0.30 mol of kobr to 1.00 l of water. the value of ka for hobr is 2.0×10−9. express your answer numerically