We place 0.123 mol of a weak acid, HA, in enough water to produce 1.00 L of solution. The final pH of the solution is 1.27 . Calculate the ionization contant, Ka, of HA.  

We place 0.647 mol of a weak acid, HA, and 11.0 g of NaOH in enough water to produce 1.00 L of solution. The final pH of this solution is 4.56 . Calculate the ionization constant, Ka, of HA.