✓ Revise Right course
Carboxylic acids end in -anoic acid, such as ethanoic acid, CH₃COOH, and butanoic acid. Free GCSE AQA Chemistry notes with key terms and 10 questions answered.
Introduction to Carboxylic Acids is part of Reactions of alkenes and alcohols (chemistry only) in GCSE AQA Higher Chemistry.
4 min
Reading time
23
Lessons in this topic
GCSE AQA Higher
Pathway
Reviewed by Revise Right
Content review
Carboxylic acids end in -anoic acid, such as ethanoic acid, CH₃COOH, and butanoic acid. Free GCSE AQA Chemistry notes with key terms and 10 questions answered.
AQA GCSE Chemistry mock draft, 26–31 Oct. Draft coverage: Chemistry Paper 1 (Higher tier). Reviewed for an original-practice sitting; check student availability before registering. Marking and results will follow later, after separate approval. Eligible new accounts receive a five-day Pro trial when signup email verification completes. Previous trials keep their original expiry. After expiry, new papers need Pro unless you have an explicitly confirmed free sitting offer for this event. That offer adds no Pro time or AI learning. Saved attempts and released results remain readable. No card or automatic charge.
Use this lesson to stay inside Reactions of alkenes and alcohols (chemistry only) while connecting the detail back to the wider Topic 7: Organic chemistry topic.
Read the core explanations from Introduction to Carboxylic Acids before testing yourself from memory.
You've probably tasted carboxylic acids without knowing it. The sharp tang in vinegar? That's ethanoic acid. The sting of ant bites? Methanoic acid. These compounds are everywhere in nature, and they all share one crucial feature that gives them their acidic bite.
The key scientific idea lies in that -COOH group. It's called a carboxyl group, and it's what transforms a simple hydrocarbon chain into an acid. Think of it as the 'acidic personality' that gets attached to different carbon chains.
Carboxylic acids form a homologous series - a family where each member has one more carbon atom than the previous one. You need to know the first four members by name, and here's the pattern that makes them clear and systematic to remember.
Notice the naming pattern: meth- (1 carbon), eth- (2 carbons), prop- (3 carbons), but- (4 carbons). The -anoic acid ending tells you it's a carboxylic acid. This pattern continues throughout organic chemistry.
Chemists are lazy in a clever way - we have shortcuts for drawing molecules. For carboxylic acids, you'll see the same molecule written in different ways. Let's use ethanoic acid as our example to show you all the acceptable formats.
The full structural formula shows every bond: CH₃-COOH. The condensed formula groups atoms together: CH₃COOH. Both are correct, and examiners accept either. The key is showing that -COOH group clearly.
Worked example: Drawing Propanoic Acid Structure
Draw the structural formula for propanoic acid showing all bonds.
Answer: CH₃CH₂COOH or CH₃-CH₂-COOH
**Trap**: Many students think the carbon in -COOH doesn't count towards the total. It does! Methanoic acid (HCOOH) has 1 carbon total - that's the carbon in the -COOH group.
In exams, you'll need to identify carboxylic acids from their names or formulae. Here's your recognition toolkit. The giveaway is always that -COOH group, but it might be hidden in different ways.
From names: Look for '-anoic acid' ending. Methanoic, ethanoic, propanoic, butanoic - they all follow this pattern. From formulae: Hunt for the -COOH group. It might be written as COOH, -COOH, or even CO₂H in some textbooks.
Carboxylic acid questions are usually straightforward, but students lose marks through careless errors. Here's how to avoid the common traps and secure every available mark.
**Command word focus**: 'Identify' means point out or name. 'Draw' means show the structure with bonds. 'State' means give the name without explanation. Match your answer to what's being asked.
Exam precision note: In Introduction to Carboxylic Acids - Carboxylic acids - Introduction to carboxylic acids, always identify the key chemical idea first, then link it to evidence, data, or an equation. A high-scoring GCSE answer names the particles involved, states what changes, and justifies the conclusion using correct scientific language. Where calculations are used, show each step with units and keep significant figures sensible. Finally, check that terminology matches AQA wording so your answer is unambiguous and mark-scheme friendly.
Ethanoic acid can be written as CH3COOH. The COOH functional group is what makes it a carboxylic acid, and this group is responsible for the acidic reactions students meet at GCSE. The common name acetic acid is still often used for the acid found in vinegar.
Published by Revise Right. Use the official specification reference to check the requirements for your course. Content updated: 2026-03-19.
Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.
The formula of ethanoic acid is CH₃COOH. It is the carboxylic acid with 2 carbons, commonly known as the acid in vinegar, and its common name acetic acid is still often used.
Butanoic acid, CH₃CH₂CH₂COOH, is responsible for the smell of rancid butter. It is the fourth carboxylic acid, with 4 carbons including the carbon in the -COOH group.
The first four carboxylic acids are methanoic acid (HCOOH), ethanoic acid (CH₃COOH), propanoic acid (CH₃CH₂COOH) and butanoic acid (CH₃CH₂CH₂COOH). Their names all end in -anoic acid.
Carboxylic acids are named with a prefix for the number of carbons, meth- (1), eth- (2), prop- (3) or but- (4), and the ending '-anoic acid'. The carbon in the -COOH group counts, giving methanoic, ethanoic, propanoic and butanoic acid.
The functional group of carboxylic acids is -COOH, called the carboxyl group. It gives carboxylic acids their acidic properties and the ability to form salts with metals and bases.
The acid in vinegar is ethanoic acid, CH₃COOH, a carboxylic acid also commonly called acetic acid. Methanoic acid, the simplest carboxylic acid, is found in ant and nettle stings.
The carbon in the -COOH group counts towards the total number of carbons when naming a carboxylic acid. Methanoic acid (HCOOH) has 1 carbon, which is the carbon in the -COOH group, and propanoic acid has 3 carbons in total.
A carboxylic acid can be recognised by a name ending in -anoic acid or by a -COOH group in its formula, which may also be written as CO₂H. For example, CH₃CH₂COOH is propanoic acid.
Methanoic acid is the acid in ant stings and nettle stings. Its formula is HCOOH, making it the simplest carboxylic acid, with just one carbon atom, the one in the -COOH group.
Propanoic acid, CH₃CH₂COOH, is used as a food preservative. It is the third member of the carboxylic acid homologous series, with 3 carbon atoms including the one in the -COOH group.