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Experimental Techniques

Standard solutions, titrations and qualitative tests

  • 3 things to know
  • AS 1

Overview

Standard solutions and volumetric flasks, titration apparatus, concordant titres and a mean titre, moles in solution, flame test colours and the silver nitrate test for halides.

What you need to know

Answer each one before you reveal it.

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Key term

Which flame colours do lithium, sodium, potassium, calcium and copper ions give, and how are halide ions identified?

Key term

What is a standard solution?

Key term

How is a standard solution prepared?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is a standard solution?

    Model answer

    A standard solution is a solution whose concentration is known accurately. The solution is made by dissolving a weighed mass of solute and making it up to a known volume.

  2. 2

    How is a standard solution prepared?

    Model answer

    The solid is weighed accurately, dissolved in distilled water in a beaker and transferred to a volumetric flask with all rinsings. Distilled water is added to the graduation mark and the flask is inverted to mix.

  3. 3

    Why is a volumetric flask used to make a standard solution?

    Model answer

    A volumetric flask holds a precise volume at its graduation mark. The concentration can then be calculated accurately.

  4. 4

    What is a titration?

    Model answer

    A titration is a technique that measures the exact volume of one solution needed to react with a known volume of another. An indicator shows the end point.

  5. 5

    What apparatus is used in an acid–base titration?

    Model answer

    A pipette measures a fixed volume of one solution into a conical flask, and a burette adds the other solution. An indicator shows the end point.

  6. 6

    What are concordant titres?

    Model answer

    Concordant titres are results that agree closely, usually within 0.10 cm³ of each other. The mean of concordant titres is used in calculations.

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