---
title: "Carboxylic Acids, Esters and Hydrolysis"
description: "Carboxylic acids are weak acids that still fizz with carbonates, and with an alcohol they form an ester in a reaction that never quite finishes. Hydrolysis runs the ester back, in acid or in alkali."
canonical: https://lightmysky.com/learn/science/carboxylic-acids-esters-and-hydrolysis-mt_QLxUs5cOH2
source: https://lightmysky.com/learn/science/carboxylic-acids-esters-and-hydrolysis-mt_QLxUs5cOH2.md
retrieved: 2026-11-12
---

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# Carboxylic Acids, Esters and Hydrolysis

Carboxylic acids are weak acids that still fizz with carbonates, and with an alcohol they form an ester in a reaction that never quite finishes. Hydrolysis runs the ester back, in acid or in alkali.

Subject: Science · Area: Chemistry · Ages 17 to 18
Page: https://lightmysky.com/learn/science/carboxylic-acids-esters-and-hydrolysis-mt_QLxUs5cOH2

## Ready when they can

- Writes the reactions of a carboxylic acid with a carbonate, with a metal and with an alkali
- Explains why a carboxylic acid counts as weak and is still acidic enough to release carbon dioxide
- Writes esterification with its catalyst and explains why the yield is limited
- Compares acid hydrolysis with alkaline hydrolysis of an ester and gives a use for each

## Lesson: Acids, esters and hydrolysis

Pour vinegar onto baking soda and it fizzes at once. Vinegar carries acetic acid and baking soda is a carbonate, and acid plus carbonate gives a salt plus water plus carbon dioxide. With a reactive metal such as magnesium, a carboxylic acid gives a salt and hydrogen. With an alkali it gives a salt and water.

Acetic acid is weak, with only about 1 in 100 split at a time, yet the fizz still finishes. Each used-up H+ is topped up from the waiting molecules, so weak never meant too weak to react.

**Example.** Warm acetic acid with ethanol and an acid catalyst, usually concentrated sulfuric acid, and you get ethyl acetate, the fruity ester, plus water. The name has two parts: ethyl from the alcohol, then acetate from the acid. The catalyst speeds the reaction up, but the reaction also runs backwards, so the reaction never goes to completion.

Hydrolysis runs the ester back. With acid you get the carboxylic acid and the alcohol again, and like esterification this stops short of completion. With sodium hydroxide you get the alcohol and the salt of the acid instead, and the reaction goes to completion. That alkaline route is how fats are turned into soap.

**Recap.** Weak acids still fizz with carbonates, ester-making never finishes, and the hydrolysis route decides whether you get the salt or the acid.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Aldehydes and Ketones: Nucleophilic Addition and the Tests That Separate Them](https://lightmysky.com/learn/science/aldehydes-and-ketones-nucleophilic-addition-and-the-tests-that-separate-them-mt_bVcJ0UaXk6)

## Optional connections

- [The Equilibrium Constant Kc](https://lightmysky.com/learn/science/the-equilibrium-constant-kc-mt_3G8b6Hyz3u)
- [Weak Acids, Ka and pKa](https://lightmysky.com/learn/science/weak-acids-ka-and-pka-mt_q7fYb7qzMH)

## Opens up

- [Nucleophilic Acyl Substitution and the Reactivity Ladder](https://lightmysky.com/learn/science/nucleophilic-acyl-substitution-and-the-reactivity-ladder-mt_b60fq2aQ7r)
- [Addition and Condensation Polymers](https://lightmysky.com/learn/science/addition-and-condensation-polymers-mt_klu208vTI1)