Select indicators from Table 16-2 that would be suitable for finding the end point in Figure 16-3. What color changes would be observed?

Indicators are weak acids or bases (typically derived from plant pigments) that have unique colors in their ionized and non-ionized states and are proportional to the pH of the solution being tested.

A material that can be added to the reaction mixture to show the titration's equivalence point. pH is frequently measured with colored indicators.

The potential of the indicator should overlap with the steep part of the curve. The potential for redox indicators is with respect to standard hydrogen electrode.

• Since there is standard calomel $16-3$, to find the potential with respect to standard calomel electrode, we need to subtract the potential from the table with the potential of standard calomel electrode (0.241V ).

• The most suitable indicators are:

• Ferroin: potential around $0.91\mathrm{V}\Rightarrow$color change from pale blue to red

• Tris (2,2'-bipyridine)iron: potential around $0.88\mathrm{V}\Rightarrow$color change from pale blue to red

• Diphenylbenzidine sulfonic acid: potential around $0.63\mathrm{V}\Rightarrow$color change from violet to colorless