At pH 13, the absorbance of a certain phenol is 1.5 at 430 nm and 0.0 at 290 nm.  At pH 4, the values for a solution of the same concentration are 0.0 and 0.5, respectively.  At pH 9, the values are 0.9 and 0.4, respectively. 

 

If the concentration used was 10.8 mg of phenol in 20 ml of solvent, for an e = 300 M^-1cm^-1 in a 1.0 cm cell, calculate the molecular weight of the phenol.