10.7 : Redox Titration: Overview

Redox titration is a chemical analysis technique used to determine the concentration of an unknown substance by measuring the electron transfer in a redox (reduction-oxidation) reaction. The process involves gradually adding a titrant with a known concentration of an oxidizing or reducing agent, to the analyte, the solution with an unknown concentration, until reaching the endpoint, which indicates the completion of the reaction between the two substances. Ensuring the analyte is in a single oxidation state before titration is crucial. This can be achieved by pre-oxidizing or pre-reducing the analyte using an auxiliary reagent. Redox titrations use various types of redox indicators to determine the endpoint, including color-changing dyes and potentiometric methods employing electrodes. Visual redox indicators change color based on their oxidation state, signaling that a certain redox potential has been reached. In contrast, potentiometric methods measure the change in electrical potential across the solution using a pH or redox electrode to determine the endpoint. Self-indicators are substances that exhibit a color change due to their inherent redox properties, eliminating the need for external indicators. Starch is a commonly used visual indicator in iodometric titrations, forming a dark blue complex when it reacts with iodine. The choice of indicator in a redox titration depends on the specific reaction and the desired sensitivity and accuracy of the analysis. A titration curve is created by plotting the change in potential or the analyte's concentration against the volume of titrant added.