Explain the concept of acid-base titrations and... - SS2 Chemistry Acids, Bases, and pH Question

Acid-base titrations are analytical techniques used to determine the concentration of an unknown acid or base solution by reacting it with a standardised solution of known concentration. The process involves gradually adding the titrant solution (of known concentration) to the analyte solution (of unknown concentration) until a chemical reaction between the acid and base is complete.

In an acid-base titration, a burette is used to deliver the titrant solution in measured volumes to the analyte solution in a flask. The reaction between the acid and base is monitored using an indicator, which changes colour when the equivalence point is reached. The equivalence point occurs when the stoichiometrically equivalent amounts of acid and base have reacted. At this point, the reaction is complete, and the indicator undergoes a visible colour change.

The titration curve is a graph plotting the pH (or volume of titrant) against the volume of titrant added. It exhibits characteristic shapes based on the type of acid and base involved. The curve typically shows a gradual change in pH at the beginning, followed by a steeper slope near the equivalence point, and finally levels off after the equivalence point.

Indicators play a crucial role in acid-base titrations by providing a visual indication of the equivalence point. They undergo a colour change within a specific pH range, typically close to the equivalence point. Common indicators include phenolphthalein (pH range around 8.2-10) for weak acid-strong base titrations and methyl orange (pH range around 3.1-4.4) for strong acid-strong base titrations. By observing the colour change of the indicator, the endpoint of the titration can be determined, which corresponds to the equivalence point.