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Alcohols and Carboxylic Acids

The dichromate(VI) test for alcohols

  • 3 things to know
  • Components 1 and 2

Overview

Reagent used in the dichromate(VI) test on an alcohol, test and the observation for a primary or secondary alcohol and one safety precaution required when handling potassium dichromate(VI).

What you need to know

Answer each one before you reveal it.

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Key term

State the reagent used in the dichromate(VI) test on an alcohol.

Key term

Describe the test and the observation for a primary or secondary alcohol.

Key term

Give the reason for the colour change in the dichromate(VI) test for an alcohol

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    State the reagent used in the dichromate(VI) test on an alcohol.

    Model answer

    Potassium dichromate(VI) solution acidified with dilute sulfuric acid is used.

  2. 2

    Describe the test and the observation for a primary or secondary alcohol.

    Model answer

    A few drops of the alcohol are warmed with the acidified reagent, and the orange solution turns green.

  3. 3

    What is observed when a tertiary alcohol is warmed with acidified potassium dichromate(VI)?

    Model answer

    There is no change and the solution stays orange.

  4. 4

    Give the reason for the colour change in this test.

    Model answer

    The orange dichromate(VI) ion is reduced to the green chromium(III) ion as the alcohol is oxidised.

  5. 5

    Write the half equation for the reduction of the dichromate(VI) ion in acid solution.

    Model answer

    Cr₂O₇²⁻ + 14H⁺ + 6e⁻ → 2Cr³⁺ + 7H₂O.

  6. 6

    Give the formula and colour of the dichromate(VI) ion and of the ion it becomes.

    Model answer

    Cr₂O₇²⁻ is orange and it becomes Cr³⁺, which is green.

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