Ethanoic acid reactions: name and formulate the salts
Predict ethanoates from reactive metals, bases and carbonates, retaining the ethanoate group and the correct other products.
Section 11.7 · Carboxylic acids
Exam scope and assessment notes
Core and Extended · Chemistry 0971, 2026–2028. Manufacture comparisons, ethanol oxidation and esterification are developed in Extended lessons. Cambridge states that IGCSE 0971 has the same subject content as IGCSE 0620, with 9–1 grading. This StudyForA pathway maps the 2026–2028 syllabus only. This 9–1 graded qualification is available only in a limited number of administrative zones. Confirm that your centre can enter you for this code and exam series with Cambridge International. Cambridge has published a separate syllabus for 2029. StudyForA has not reconciled that version yet; this page supports exams in 2026, 2027 and 2028 only.
Before you begin
- Read ethanoic acid CH₃COOH and balance equations.
- Use acid reaction patterns, ion charges and brackets for repeated groups.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which gas belongs to the carbonate-plus-acid pattern?
What you will learn
- Describe ethanoic acid reactions with metals, bases and carbonates.
- Name and write formulas for the ethanoate salts and balance representative equations.
Keep the acid-derived group in the salt
Ethanoic acid CH₃COOH forms ethanoate salts. Its acid-derived ion is CH₃COO⁻. A +1 metal ion needs one ethanoate, as in sodium ethanoate CH₃COONa; a +2 metal ion needs two, as in magnesium ethanoate Mg(CH₃COO)₂ or calcium ethanoate Ca(CH₃COO)₂. The brackets multiply the whole CH₃COO group, not only the final O atom.
The salt name combines the metal name with ethanoate. Use copper(II) ethanoate for Cu(CH₃COO)₂ when the metal ion is Cu²⁺. An ethanoate salt is not an ester: CH₃COONa pairs the ion with sodium, whereas CH₃COOCH₃ has a covalently linked organic alkyl group. Later esterification develops that distinction.
Choose the other products from the reactant type
A suitable reactive metal gives an ethanoate and hydrogen: Mg+2CH₃COOH→Mg(CH₃COO)₂+H₂. Do not say every metal gives hydrogen; copper metal does not show this reaction with the stated dilute non-oxidising ethanoic-acid model. A base gives salt and water: CH₃COOH+NaOH→CH₃COONa+H₂O, or 2CH₃COOH+CuO→Cu(CH₃COO)₂+H₂O.
A carbonate gives salt, carbon dioxide and water: 2CH₃COOH+Na₂CO₃→2CH₃COONa+CO₂+H₂O. With calcium carbonate, 2CH₃COOH+CaCO₃→Ca(CH₃COO)₂+CO₂+H₂O. Ethanoic acid's weak-acid classification does not mean no acid reactions; strength describes its partial ionisation in aqueous solution, rather than an absence of acidic behaviour.
Pause and explain
Which formula matches calcium ethanoate?
Worked example
Give the name and formula of the salt from calcium carbonate and ethanoic acid, then balance all products.
Show the worked solution
- Ca²⁺ needs two CH₃COO⁻ ions, so the salt is calcium ethanoate Ca(CH₃COO)₂.
- A carbonate also gives CO₂ and H₂O.
- 2CH₃COOH+CaCO₃→Ca(CH₃COO)₂+CO₂+H₂O conserves all atoms.
Answer Calcium ethanoate Ca(CH₃COO)₂; 2CH₃COOH+CaCO₃→Ca(CH₃COO)₂+CO₂+H₂O.
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Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Predict the salt and gas from magnesium plus ethanoic acid, and balance the equation.
Give me a hint
Use the +2 metal ion and the reactive-metal acid pattern.
Compare my reasoning
- The salt is magnesium ethanoate, Mg(CH₃COO)₂.
- The suitable metal reaction gives H₂.
- Mg+2CH₃COOH→Mg(CH₃COO)₂+H₂ balances the complete products.
Magnesium ethanoate Mg(CH₃COO)₂ and hydrogen; Mg+2CH₃COOH→Mg(CH₃COO)₂+H₂.
Look for these in your work
- Salt naming and charge-balanced formula agree.
- The gas and whole equation match the metal pattern.
Give named salt products and equations for ethanoic acid with sodium hydroxide and with sodium carbonate.
Give me a hint
Only the carbonate equation includes carbon dioxide.
Compare my reasoning
- Sodium ethanoate is CH₃COONa in both reactions.
- CH₃COOH+NaOH→CH₃COONa+H₂O is neutralisation.
- 2CH₃COOH+Na₂CO₃→2CH₃COONa+CO₂+H₂O gives the carbonate's gas as well.
Sodium ethanoate CH₃COONa; CH₃COOH+NaOH→CH₃COONa+H₂O and 2CH₃COOH+Na₂CO₃→2CH₃COONa+CO₂+H₂O.
Look for these in your work
- Both salts are named and formulated.
- The different other products and coefficients are correct.
A student predicts H₂ from both copper metal and copper(II) oxide with dilute ethanoic acid. Assess both and give the oxide's salt formula and equation.
Give me a hint
The oxide is a base, while copper metal is not a suitable hydrogen-producing metal in this model.
Compare my reasoning
- Copper metal does not give the predicted hydrogen in the stated dilute non-oxidising acid model.
- Copper(II) oxide reacts as a base, forming copper(II) ethanoate Cu(CH₃COO)₂ and water.
- 2CH₃COOH+CuO→Cu(CH₃COO)₂+H₂O; neither prediction of H₂ is appropriate here.
Copper metal: no predicted H₂ in this model. CuO: copper(II) ethanoate Cu(CH₃COO)₂ and water, 2CH₃COOH+CuO→Cu(CH₃COO)₂+H₂O.
Look for these in your work
- Metal and oxide behaviour are distinguished.
- The named +2 salt, equation and water product agree.
Common mistakes
- Using chloride or sulfate as the acid-derived group for ethanoic acid.
- Writing only one ethanoate with a +2 metal ion.
- Giving hydrogen as the carbonate's gas product.
- Assuming copper metal and copper(II) oxide have the same acid reaction.
What can you explain now?
Name and formulate the salt from magnesium and ethanoic acid.
Compare with the explanation
Magnesium ethanoate, Mg(CH₃COO)₂.
A +2 magnesium ion balances two −1 ethanoate ions.
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Make it stick
Predict ethanoate names and formulas for +1 and +2 metals, then choose hydrogen, water or carbon dioxide/water from the reactant type.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.