Final answer:
For titrations, it is essential to choose an indicator with a clear and rapid color change near the expected equivalence point pH. Universal indicator and specific indicators are chosen according to the titration type, ensuring no reaction with the substance titrated and the pKin is well-matched to the anticipated endpoint pH.
Step-by-step explanation:
When conducting a titration experiment, indicators are crucial for signaling the end point via a color change. To make it easier to spot the change, one should select an indicator that has a sharp and easily detectable color change at the equivalence point. This is best achieved by choosing an indicator whose pKin is within one pH unit of the expected pH at the equivalence point, ensuring a rapid and distinct color transition. This selection is informed by titration curves and knowledge of the titration's expected endpoint.
For instance, a universal indicator is useful as it displays a wide range of colors across the pH spectrum and can be used to quickly test for approximate pH levels. Specific indicators are chosen based on whether the titration is between a strong acid and base, a weak acid and a strong base, or vice versa. The indicator selection for titrations is also dependent on ensuring that the indicator does not react with the substances being titrated, to avoid any potential errors in measurement.
Furthermore, the change in color is not abrupt but occurs over a range of about two pH units, with the most noticeable shift at an [In-]/[HIn] ratio that changes around the indicator's pKin.