4.6.2Organic Chemistry
Reactions of Carboxylic Acids — Edexcel Linear - OL (Chemistry) Revision Notes & Topical Questions
5 min read 5 parts Lesson 16 of 18 Unit quiz
Curriculum Equation Key معادلة تفاعل تكوين الإستر (الأسترة) - Esterification Reaction EquationFast Exam Solution
R-COOH + R2-OH ⇌ (conc. H₂SO₄) R-COO-R2 + H₂O
Word Equation & Conditions: حمض كربوكسيلي + كحول (في وجود حمض الكبريتيك المركز كعامل حفاز ونازع للماء) ⇌ إستر + ماء
Location & Specifications: الكيمياء العضوية للثانوية العامة والتحصيلي و Edexcel Chemistry.
Part 1 of 5Carboxylic Acids as Acids
The properties of carboxylic acids mirror those of common mineral acids, though they react more slowly.
Functional group
- Functional group Carboxylic acids contain the –COOH group, and the hydrogen can be released as H⁺ in water.
Weak acids
- Weak acids They only partially ionise, so they are weak acids with a higher pH than a strong acid of the same concentration.
Typical acid reactions
- Typical acid reactions They behave like other acids, reacting with reactive metals and with carbonates.
Naming salts
- Naming salts The salts are named by changing -oic acid to -oate, so ethanoic acid gives ethanoates.
Part 2 of 5Reaction with Metals
Reaction with Metals
General pattern
- General pattern Carboxylic acid + reactive metal → metal carboxylate + hydrogen.
Magnesium
- Magnesium 2CH₃COOH + Mg → (CH₃COO)₂Mg + H₂, forming magnesium ethanoate.
Observation
- Observation Bubbles of hydrogen are seen, which burn with a squeaky pop.
Rate
- Rate The reaction is slower than with a strong acid of the same concentration because fewer H⁺ ions are present.
| Acid | Salt name | Formula of ion |
|---|---|---|
| Methanoic | Methanoate | HCOO⁻ |
| Ethanoic | Ethanoate | CH₃COO⁻ |
| Butanoic | Butanoate | CH₃CH₂CH₂COO⁻ |
Part 3 of 5Reaction with Carbonates
Reaction with Carbonates
General pattern
- General pattern Carboxylic acid + metal carbonate → metal carboxylate + water + carbon dioxide.
Sodium carbonate
- Sodium carbonate 2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂.
Potassium carbonate
- Potassium carbonate 2CH₃CH₂CH₂COOH + K₂CO₃ → 2CH₃CH₂CH₂COOK + H₂O + CO₂.
Observation
- Observation The mixture fizzes, and the gas turns limewater cloudy.
Part 4 of 5Writing an Equation
1
Identify the acid and write its formula with the –COOH group shown.
2
Name the salt by replacing -oic acid with -oate and adding the metal name first.
3
Write the formula of the salt, with the metal replacing the hydrogen of the –COOH group.
4
Balance the equation, remembering that each –COOH loses one hydrogen.
5
Add the other products: hydrogen for metals, or water and carbon dioxide for carbonates.
Part 5 of 5Exam Checklist & Tips
4.6.2 – Key Points for the Exam
- Carboxylic acid An organic compound containing the –COOH functional group.
- Weak acid An acid that is only partially ionised in water.
- Carboxylate The salt formed from a carboxylic acid, with name ending -oate.
- Functional group The atom or group of atoms that determines the reactions of an organic compound.
Common Mistakes
- Naming the salt as ethanoic instead of ethanoate.
- Forgetting that two moles of acid are needed per mole of carbonate.
- Saying carboxylic acids are strong acids.
- Missing the water in the products of the carbonate reaction.
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