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Core: Describe an acid–base titration to include the use of a:
Core: Describe how to identify the end-point of a titration using an indicator
An acid–base titration is a method of quantitative chemical analysis where an acid is added slowly to a base until it has been neutralised. This technique allows us to determine the concentration of acidic or alkaline solutions with high precision.
Quantitative analysis refers to the process used to determine the amount or percentage of a substance in a given sample. Titrations are widely used across many industries including:
A volumetric pipette is used to measure a fixed, accurate volume of the base solution. The base is placed into a conical flask using the pipette with a filler (never use your mouth).
Common pipette volumes:
A burette is a piece of glassware that delivers an accurate but variable volume of liquid. The acid solution is dispensed from the burette.
Key features:
The conical flask contains the base solution (from the pipette) and the indicator. It must be swirled during the titration to ensure the reactants are thoroughly mixed and the reaction is complete.
A white tile is placed under the conical flask to help observe any colour change in the indicator clearly.
An indicator is a substance that changes colour when added to acidic or alkaline solutions. The indicator helps identify when neutralisation is complete.
Colour change:
Colour change:
Important Note: Methyl orange and thymolphthalein have sharp, distinct colour changes at specific pH levels, making them suitable for titrations. Universal Indicator is not suitable because it has a gradual colour change over a wide pH range, making it difficult to identify a precise end-point.
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