Ethanoic acid

The idea

Ethanoic acid, commonly called acetic acid, is a carboxylic acid; a 5-8% solution of it in water is vinegar, and pure ethanoic acid, which melts at 290 K and freezes in cold climates, is called glacial acetic acid.

In the pickle jar

Vinegar is used widely as a preservative in pickles. It is a solution of a carboxylic acid in water.

What is that carboxylic acid commonly called?

• Acetic acid
• Absolute alcohol
• Sodium ethoxide

Ethanoic acid

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Names and numbers

Ethanoic acid and acetic acid are two names for the same carboxylic acid. Its solution in water is vinegar, and the pure acid can freeze.

Ethanoic acid, commonly called acetic acid, is a carboxylic acid. A 5 to 8% solution of it in water is vinegar, and pure ethanoic acid, which melts at 290 K and freezes in cold climates, is called glacial acetic acid.

Notes

Ethanoic acid, commonly called acetic acid, is a carboxylic acid. A 5 to 8% solution of it in water is vinegar; pure ethanoic acid, which melts at 290 K, is called glacial acetic acid.

Check yourself

What is another common name for ethanoic acid?

What is a 5 to 8% solution of acetic acid in water called?

What is the melting point of pure ethanoic acid, in kelvin?

Answer: 290 K

The melting point of pure ethanoic acid is 290 K.

Why is pure ethanoic acid called glacial acetic acid?

• Absolute alcohol. Absolute alcohol is pure ethanol.
• Acetic acid — correct. Yes!
• Sodium ethoxide. Sodium ethoxide is a product of ethanol and sodium.
• Glacial acetic acid. Glacial acetic acid is pure ethanoic acid, not a solution in water.
• Absolute alcohol. Absolute alcohol is pure ethanol.
• Vinegar — correct. Yes!
• It melts at 290 K, so it often freezes in winter in cold climates — correct. Yes!
• It is always found as a gas. Pure ethanoic acid melts at 290 K, and it freezes in cold climates, which gave it the name.
• It is a solution in water. Pure ethanoic acid is not a solution. A 5 to 8% solution in water is vinegar.