Ethanoic acid
A bottle of vinegar keeps pickles safe for months.
Pick an acid. Drop in zinc. Watch the fizz.
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The rule
Ethanoic acid is a weak acid. It frees fewer H⁺ than a strong acid. Weak does not mean harmless.
Ethanoic acid, CH₃COOH, is a carboxylic acid. In water only some of its molecules free H⁺. That is why it is weak. Hydrochloric acid frees nearly all of its H⁺. That is a strong acid.
Weak and dilute are different. Dilute tells how much acid is in the water. Weak tells how many H⁺ it frees.
| Property | The record |
|---|---|
| In water | A weak acid. It turns blue litmus red. |
| A 5 to 8 percent solution in water | Vinegar. It preserves pickles. |
| Pure, below about 17 °C | It freezes to a solid. This is glacial acetic acid. |
Ethanoic acid fizzes with baking soda and gives carbon dioxide. Ethanol does not. That tells the two apart.
A teacher warms ethanoic acid with ethanol and a little strong acid. An ester forms.