18. Aqueous Equilibrium

Chemistry student is using an indicator with a pK_a of 4.7 for the titration of a strong acid with strong base. Calculate the pH range at which the indicator will change colors.

a) 2.7–3.5                      b) 10–11                        c) 4.7–8.7                      d) 3.7–5.7                      e) 2.7–5.8

Bromophenol blue (pK_a = 4.1) is a common acid-base indicator. It is yellow in its acidic form and blue in conjugate base form. If the solution being titrated has a pH = 4.0, what color would the bromophenol blue indicator possess?

a) yellow                       b) orange                      c) blue                          d) green                      e) purple 

When CO₂ combines with water it forms carbonic acid. How does this explain the phenol red result?

A substance that changes color in the presence of an acid or base is called a(n)