Titration at the Pink Endpoint

In the picture

1. 1Burette stopcock: controls the dropwise addition of titrant.
2. 2Meniscus at the graduation mark: gives the burette reading before the last small addition.
3. 3White tile under the flask: creates a bright background for judging the colour change.
4. 4Pale-pink swirl in the flask: shows the first local excess of titrant after the reaction.
5. 5Liquid line in the conical flask: shows the bulk solution is still almost colourless while the pink streak spreads.

Examples

• Finding the acid concentration of vinegar with a sodium hydroxide solution in a school laboratory.
• Checking the acid content of a fruit juice or a cleaning product before it is bottled.

Quiz: Titration at the Pink Endpoint (Age 17)

1. 1

   What is the difference between the endpoint and the equivalence point in this titration?

   • The endpoint and the equivalence point always occur at exactly the same volume.
   • The endpoint is the true stoichiometric point, while the equivalence point is the observed colour change.
   • The endpoint is the observed colour change, while the equivalence point is the true stoichiometric point.
2. 2

   At the equivalence volume, what happens to the limiting reactant?

   • It stays limiting even after the equivalence volume.
   • It is no longer involved in the reaction.
   • It switches from one reactant to the other.
3. 3

   What can the volume added at the endpoint be used to calculate?

   • The exact colour of the indicator at the start.
   • The mass of the conical flask after titration.
   • The unknown concentration of the solution being analysed.

The answers, each with its explanation, are in the app. This lesson has left the free week, so its quiz is part of the subscription.