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Acid-Base Titrations

Titration technique, mean titres and uncertainty

  • 3 things to know
  • Unit AS 1

Overview

How a burette is read correctly, purpose of the first rough titration and concordant titres.

What you need to know

Answer each one before you reveal it.

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Key term

Why are the inside walls of the conical flask washed down with distilled water near the end point?

Key term

Why is a burette rinsed with the solution it is to contain before a titration?

Key term

Why is the conical flask rinsed only with distilled water?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Why is a burette rinsed with the solution it is to contain before a titration?

    Model answer

    Any distilled water left in the burette would dilute the solution and make the titre larger than it should be.

  2. 2

    Why is the conical flask rinsed only with distilled water?

    Model answer

    The flask holds a measured amount of solution delivered by the pipette, so rinsing it with that solution would add extra moles and change the titre.

  3. 3

    Describe how a burette is read correctly.

    Model answer

    The bottom of the meniscus is read at eye level against the graduations, to avoid a parallax error.

  4. 4

    Why is a white tile placed under the conical flask?

    Model answer

    A white background makes the first permanent change of indicator colour much easier to see.

  5. 5

    Why is the conical flask swirled continuously during a titration?

    Model answer

    Swirling mixes the added solution thoroughly, so that a local excess is not mistaken for the end point.

  6. 6

    Why are the inside walls of the conical flask washed down with distilled water near the end point?

    Model answer

    Any splashes on the walls have not yet reacted, and washing them in makes sure all of the solution delivered has taken part, while the added water does not change the number of moles.

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