23.84 ml of a pb2 solution, containing excess pb2 , was added to 12.75 ml of a 2,3-dimercapto-1-propanol (bal) solution of unknown concentration, forming the 1: 1 pb2 –bal complex. the excess pb2 was titrated with 0.0126 m edta, requiring 9.68 ml to reach the equivalence point. separately, 38.51 ml of the edta solution was required to titrate 30.75 ml of the pb2 solution. calculate the bal concentration, in molarity, of the original 12.75-ml solution.