A solution of a weak acid, HA, is prepared by dissolving 4.8 mmol of HA in 10.0 liters of a solution.
The following values of absorbances were measured in a 1.0 cm cell in various buffers.
pH: 1.00, A=1.25
pH:2.00, A= 1.25
pH:7.38, A=0.45
pH:11.0, A= 0.29
pH:12.0, A=0.29
a) Assuming that at low pH the principle species in solution is HA and at high pH the principle species is A-, calculate the pKa of the indicator.
b) calculate the absorbance at pH 6.50.