Carboxylic acids
| English | Chinese | Pinyin |
|---|---|---|
| carboxylic acid | 羧酸 | suō suān |
| ethanoic acid | 乙酸 | yǐ suān |
| weak acids | 弱酸 | ruò suān |
| esters | 酯 | zhǐ |
The sour family
- The sharp taste of vinegar comes from a carboxylic acid 羧酸.
- They are a homologous series with the –COOH functional group.
The functional group of carboxylic acids is:
Carboxylic acids contain –COOH.
The carboxylic acid found in vinegar is:
Ethanoic acid (CH₃COOH) is in vinegar.
The carboxylic acid functional group is written –______.
It is the carboxyl group.
The carboxylic acid family
- Carboxylic acids contain the –COOH functional group.
- Example: ethanoic acid 乙酸 (CH₃COOH), the acid in vinegar.
Carboxylic acids share the –COOH (carboxyl) functional group, as in ethanoic acid
A weak acid's pH
Carboxylic acids are weak acids — they only partly ionise, so they sit just below pH 7. Slide the scale to see where they fall.
Carboxylic acids are described as weak acids because they:
Weak means partly ionised, not dilute.
Match each carboxylic-acid fact.
Carboxylic acids contain –COOH, are weak acids, and fizz with carbonates.
Weak acids 弱酸
- Carboxylic acids are weak acids: they only partly ionise in water.
- They still show typical acid reactions, just less vigorously than strong acids.
A carboxylic acid and an alcohol react to make an ester and water
A carboxylic acid reacts with an alcohol to form a sweet-smelling:
Acid + alcohol → ester.
Reactions
- They react with metals (→ salt + hydrogen) and carbonates (→ salt + water + CO₂).
- They react with alcohols to form sweet-smelling esters 酯.
Carboxylic acids are weak acids. Unlike hydrochloric acid (strong, fully ionised), they only partly ionise — so they react more gently. "Weak" describes ionisation, not concentration.
You've got it
- carboxylic acids have the –COOH group (e.g. ethanoic acid in vinegar)
- they are weak acids (only partly ionise) but show typical acid reactions
- they react with metals, carbonates, and with alcohols to form esters