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Chemistry
3 Dec 2025
154
4 pages
Carboxylic acids are everywhere around you - from the vinegar in your chips to the citric acid in... Show more
The functional group that defines carboxylic acids is -COOH, which gives them their distinctive properties. When naming these compounds, you simply add the suffix -oic acid to the end (like ethanoic acid for vinegar).
If a molecule has two carboxylic acid groups, you use -dioic acid instead. Think of it as doubling up on the acidity! The general structure shows a carbon atom bonded to both a hydroxyl group and a carbonyl group .
The geometry around the carbon is particularly important - you'll find three regions of electron density creating bond angles of 120°, whilst the oxygen in the -OH group has two bonded pairs and two lone pairs, giving it a 104.5° angle.
Key Insight The -COOH group combines two familiar functional groups (carbonyl and hydroxyl), which explains why carboxylic acids are so reactive and versatile.
Hydrogen bonding is the secret behind carboxylic acids' unique physical properties. The polar O-H bond allows these molecules to form strong hydrogen bonds with each other, creating dimers (pairs of molecules stuck together).
This hydrogen bonding also means carboxylic acids can bond effectively with water molecules. Carboxylic acids with up to 4 carbon atoms dissolve completely in water, but solubility drops dramatically as the carbon chain gets longer.
Here's the pattern you need to remember longer carbon chains mean stronger London forces due to more electrons. This increases boiling points but decreases water solubility because the non-polar carbon chain dominates. However, if you've got more than one -COOH group, solubility increases again.
Exam Tip Remember that melting and boiling points are unusually high for carboxylic acids due to that hydrogen bonding - this often comes up in exam questions!
Carboxylic acids are weak acids, which means they only partially dissociate in water. For example, methanoic acid (HCOOH) splits into H⁺ and HCOO⁻ ions, but not completely - that's why we use the equilibrium arrow.
Since they're acids, they undergo typical acid reactions. With metals, you get a salt plus hydrogen gas (a redox reaction). With bases, you get neutralisation reactions producing a salt plus water.
The naming pattern for the salts is straightforward - just change the '-oic acid' ending to '-oate'. So ethanoic acid becomes ethanoate, propanoic acid becomes propanoate, and so on.
Memory Aid Think of carboxylic acids as "polite acids" - they donate protons, but not too aggressively, unlike strong acids like hydrochloric acid.
When carboxylic acids react with metals like magnesium, you get a classic redox reaction. For instance, propanoic acid + magnesium produces magnesium propanoate and hydrogen gas. The metal gets oxidised (loses electrons) whilst the hydrogen ions get reduced.
Neutralisation reactions follow predictable patterns. With metal oxides like calcium oxide, you get the metal carboxylate plus water. With hydroxides like sodium hydroxide, same result - salt plus water.
The test tube test for carboxylic acids uses sodium carbonate. If you add Na₂CO₃ to a carboxylic acid, you'll see fizzing as CO₂ gas is produced. This fizzing is your definitive test for the presence of a -COOH group.
Practical Note That fizzing test with sodium carbonate is dead useful for identifying unknown compounds in your practicals - if it fizzes, you've likely got a carboxylic acid!
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
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Explore the fundamentals of buffer solutions, including preparation methods, the role of weak acids and their conjugate bases, and calculations for pH using the Henderson-Hasselbalch equation. This summary covers key concepts such as acid dissociation constant (Ka), buffer capacity, and the equilibrium shifts in response to added acids or alkalis. Ideal for students studying chemistry and seeking to understand the principles behind buffer systems.
ChemistryExplore the fundamentals of acids and alkalis, including the pH scale, properties of common acids and bases, and the process of salt formation through neutralization reactions. This summary covers key concepts such as strong and weak acids, polyatomic ions, and practical applications in chemistry. Ideal for students preparing for exams or seeking to deepen their understanding of acid-base chemistry.
ChemistryThis tackles the general properties of acids and bases, their examples and pH concept.
ChemistryApp Store
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Carboxylic acids are everywhere around you - from the vinegar in your chips to the citric acid in your fizzy drinks. Understanding their structure and reactions is crucial for your A-level chemistry success, and once you grasp the basics, you'll... Show more
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The functional group that defines carboxylic acids is -COOH, which gives them their distinctive properties. When naming these compounds, you simply add the suffix -oic acid to the end (like ethanoic acid for vinegar).
If a molecule has two carboxylic acid groups, you use -dioic acid instead. Think of it as doubling up on the acidity! The general structure shows a carbon atom bonded to both a hydroxyl group and a carbonyl group .
The geometry around the carbon is particularly important - you'll find three regions of electron density creating bond angles of 120°, whilst the oxygen in the -OH group has two bonded pairs and two lone pairs, giving it a 104.5° angle.
Key Insight: The -COOH group combines two familiar functional groups (carbonyl and hydroxyl), which explains why carboxylic acids are so reactive and versatile.
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Hydrogen bonding is the secret behind carboxylic acids' unique physical properties. The polar O-H bond allows these molecules to form strong hydrogen bonds with each other, creating dimers (pairs of molecules stuck together).
This hydrogen bonding also means carboxylic acids can bond effectively with water molecules. Carboxylic acids with up to 4 carbon atoms dissolve completely in water, but solubility drops dramatically as the carbon chain gets longer.
Here's the pattern you need to remember: longer carbon chains mean stronger London forces due to more electrons. This increases boiling points but decreases water solubility because the non-polar carbon chain dominates. However, if you've got more than one -COOH group, solubility increases again.
Exam Tip: Remember that melting and boiling points are unusually high for carboxylic acids due to that hydrogen bonding - this often comes up in exam questions!
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Carboxylic acids are weak acids, which means they only partially dissociate in water. For example, methanoic acid (HCOOH) splits into H⁺ and HCOO⁻ ions, but not completely - that's why we use the equilibrium arrow.
Since they're acids, they undergo typical acid reactions. With metals, you get a salt plus hydrogen gas (a redox reaction). With bases, you get neutralisation reactions producing a salt plus water.
The naming pattern for the salts is straightforward - just change the '-oic acid' ending to '-oate'. So ethanoic acid becomes ethanoate, propanoic acid becomes propanoate, and so on.
Memory Aid: Think of carboxylic acids as "polite acids" - they donate protons, but not too aggressively, unlike strong acids like hydrochloric acid.
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When carboxylic acids react with metals like magnesium, you get a classic redox reaction. For instance, propanoic acid + magnesium produces magnesium propanoate and hydrogen gas. The metal gets oxidised (loses electrons) whilst the hydrogen ions get reduced.
Neutralisation reactions follow predictable patterns. With metal oxides like calcium oxide, you get the metal carboxylate plus water. With hydroxides like sodium hydroxide, same result - salt plus water.
The test tube test for carboxylic acids uses sodium carbonate. If you add Na₂CO₃ to a carboxylic acid, you'll see fizzing as CO₂ gas is produced. This fizzing is your definitive test for the presence of a -COOH group.
Practical Note: That fizzing test with sodium carbonate is dead useful for identifying unknown compounds in your practicals - if it fizzes, you've likely got a carboxylic acid!
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
3
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the fundamentals of buffer solutions, including preparation methods, the role of weak acids and their conjugate bases, and calculations for pH using the Henderson-Hasselbalch equation. This summary covers key concepts such as acid dissociation constant (Ka), buffer capacity, and the equilibrium shifts in response to added acids or alkalis. Ideal for students studying chemistry and seeking to understand the principles behind buffer systems.
ChemistryExplore the fundamentals of acids and alkalis, including the pH scale, properties of common acids and bases, and the process of salt formation through neutralization reactions. This summary covers key concepts such as strong and weak acids, polyatomic ions, and practical applications in chemistry. Ideal for students preparing for exams or seeking to deepen their understanding of acid-base chemistry.
ChemistryThis tackles the general properties of acids and bases, their examples and pH concept.
ChemistryApp Store
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Sociology