Why must aqueous base be added to isolate the 4-bromo-2-chloroaniline from the aqueous acidic mixture

po-215 i got it right on the quiz

a pan containing water is placed in a positio n where it is exposed to a 10 mile per hour wind. the pan contains a uniform depth of 1.27 cm of water, is quite wide, and has a length of 2.44 m in the wind direction. the water in the pan is at a constant temperature of 15.5 °c.