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Alcohols and Carboxylic Acids

Carboxylic acids and the sodium hydrogencarbonate test

  • 3 things to know
  • Components 1 and 2

Overview

Why carboxylic acids are classed as weak acids, sodium hydrogencarbonate test and the positive result and carboxylic acid with one carbon atom and give its formula.

What you need to know

Answer each one before you reveal it.

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Key term

Give the formula of the carboxyl functional group.

Key term

Write the equation for the partial dissociation of ethanoic acid in water.

Key term

Explain why carboxylic acids are classed as weak acids.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Give the formula of the carboxyl functional group.

    Model answer

    The group is —COOH.

  2. 2

    Name the carboxylic acid with two carbon atoms and give its shortened formula.

    Model answer

    It is ethanoic acid, CH₃COOH.

  3. 3

    Write the equation for the partial dissociation of ethanoic acid in water.

    Model answer

    CH₃COOH(aq) ⇌ H⁺(aq) + CH₃COO⁻(aq).

  4. 4

    Explain why carboxylic acids are classed as weak acids.

    Model answer

    Only a small proportion of the molecules release their hydrogen ion in aqueous solution, so an equilibrium is set up rather than complete dissociation.

  5. 5

    Describe the sodium hydrogencarbonate test and the positive result.

    Model answer

    Solid sodium hydrogencarbonate or its solution is added to the sample, and vigorous effervescence shows that a carboxylic acid is present.

  6. 6

    Write the equation for the reaction of ethanoic acid with sodium hydrogencarbonate.

    Model answer

    CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂.

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