Ii) Phenolphthalein is a weak acid indicator. In acidic solutions, the equilibrium HIn(aq) H^+(aq) + In^-(aq) shifts to the left, and the indicator exists p

Here are the solutions to the questions:

ii) Phenolphthalein is a weak acid indicator. In acidic solutions, the equilibrium $\text{HIn}(aq) \rightleftharpoons \text{H}^+(aq) + \text{In}^-(aq)$ shifts to the left, and the indicator exists predominantly in its undissociated, colourless form ($\text{HIn}$). As a base is added during the titration, $\text{H}^+$ ions are neutralized, causing the pH to increase. At the end point, when the solution becomes slightly alkaline (pH 8.2-10), the equilibrium shifts to the right. The $\text{HIn}$ dissociates to form $\text{In}^-$, which is the red/pink coloured form. This shift causes the solution to change from colourless to red/pink.