Carboxylic Acids, Esters and Hydrolysis · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.
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Acids, esters and hydrolysis

Science · Chemistry · ages 17-18
Name ______________________   Date ____________

  1. Acetic acid plus methanol gives which ester?

    • Methyl formate
    • Ethyl acetate
    • Methyl acetate

  2. What are the three products when a carboxylic acid meets a carbonate?

    • Salt, water and carbon dioxide
    • Salt, hydrogen and carbon dioxide
    • Ester, water and carbon dioxide

  3. Esterification with acid and alcohol goes to completion if you wait long enough.

    Circle one:   True   False

  4. What changes when an ester is hydrolysed with sodium hydroxide instead of acid?

    • You get the salt instead of the free carboxylic acid
    • You get a ketone instead of an alcohol
    • Nothing changes, since both routes match

  5. Why is acetic acid still able to fizz with carbonate despite being weak?

    • It is fully split like a strong acid
    • Used H+ is topped up from unsplit molecules
    • Carbonates react with water instead of acid

  6. Why is the yield of ethyl acetate limited?

    • The ethanol boils away before it can react
    • It also runs backwards
    • The acid catalyst is used up halfway

  7. A maker wants soap from fats. Which hydrolysis route should they pick, and why?

    • Acid hydrolysis, since it returns the free acid
    • Alkaline hydrolysis, since it gives the salt
    • Dry heating, since water ruins the fat

  8. A student says ethanoic acid is too weak to react fully with magnesium ribbon, even with the acid in excess. What should they expect to see?

    • Nothing, because the weak acid holds its H+
    • A brief fizz, then it stops with magnesium left
    • The magnesium keeps fizzing until it is used up
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Acids, esters and hydrolysis W1-mt_QLxUs5cOH2-s1

  1. Methyl acetate · Acetic acid with methanol gives methyl acetate plus water.
  2. Salt, water and carbon dioxide · The fizz is carbon dioxide, left with a salt and water.
  3. False · The reaction also runs backwards, so the reaction never goes to completion. The sentence is false.
  4. You get the salt instead of the free carboxylic acid · Alkali turns the acid part into its salt, while acid hydrolysis returns the free acid.
  5. Used H+ is topped up from unsplit molecules · Only a small share is split at once, but the store keeps refilling as H+ is used.
  6. It also runs backwards · Esterification is reversible, so product and starting materials settle into a mix.
  7. Alkaline hydrolysis, since it gives the salt · Fats are esters, and alkaline hydrolysis turns their acid parts into salts, the basis of soap.
  8. The magnesium keeps fizzing until it is used up · Each H+ used by the magnesium is replaced as more acid molecules split, so with acid in excess the reaction runs until the magnesium is gone.
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