[bull3396945]

hi,
i was doing my assignment and got stuck with these two question...if anyone could just tell me what to do? As in how to solve these questions. The guidelines but not the answer!!
Thanks and reli appreciate



1.   The pH indicator HIn has an acid dissociation constant of 4.80 x 10 -6 at 25 oC.  The accompanying 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 solutions. 

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


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

   (b)  Several buffer solutions were made 1.00 x 10 -4 M in total indicator concentration.  Absorbance data (1.00 cm cells) are shown below.  Calculate the pH of each solution.

   Solution      A (450 nm)      A (595 nm)
   A         0.344         0.310
   B         0.508         0.212
   C         0.653         0.136
   D         0.220         0.380


2.   Draw the dominant forms of each of the compounds below and state which, if any, would be expected to extract from aqueous solution into hexane at (a) pH 12 and (b) pH 2.

            CH3CH2COOH
            CH3CH2NH2
            CH3CH2CH2OH
            H2NCH2CH2COOH

[Golden_4_Life]

At pH of 12 both of your carboxylic acids will have ionized and fall out of solution into the non-polar phase.