The indicator HIn has an acid dissociation constant of 4.80 x 10^-6 at ordinary temperatures. The accompanying absorbance data are for 8.00 x 10^-5 M solutions of the indicator measured in 1.00-cm cells in strongly acidic and strongly alkaline media:

Estimate the wavelength at which absorption by the indicator becomes independent of pH (that is, the isosbestic point).

Transcribed Image Text:

Absorbance A, nm pH 1.00 pH 13.00 420 0.535 0.050 0.068 445 0.657 450 0.658 0.076 455 0.656 0.085 0.116 470 0.614 510 0.353 0.223 550 0.119 0.324 570 0.068 0.352 585 0.044 595 610 0.360 0.361 0.355 0.032 0.019 0.014 650 0.284