posted by Chrissy .
An indicator has the reaction
HIn(aq)<-->+In-(aq). Explain how the indicator can change color when a strong acid is poured into a solution of this indicator.
Did you intend to write
HIn(aq) <==> H^+(aq) + In^-(aq)
addition of H^+ from an acid causes the equilibrium to shift which way? to the left? And this changes the HIn/In^- ratio.