2- Reactions forming salts

What can carboxylic acids react with to form salts?

Metals, alkalis and carbonates.

What are the products when a carboxylic acid reacts with a metal?

Salt + hydrogen.

Write the reaction of ethanoic acid with sodium.

2CH₃CO₂H + 2Na → 2CH₃CO₂⁻Na⁺ + H₂.

What are the products when a carboxylic acid reacts with an alkali?

Salt + water.

Write the reaction of ethanoic acid with sodium hydroxide.

CH₃CO₂H + NaOH → CH₃CO₂⁻Na⁺ + H₂O.

What are the products when a carboxylic acid reacts with a carbonate?

Salt + water + carbon dioxide.

Write the reaction of ethanoic acid with sodium carbonate.

2CH₃CO₂H + Na₂CO₃ → 2CH₃CO₂⁻Na⁺ + H₂O + CO₂.

What observation occurs when a carboxylic acid reacts with a carbonate?

Effervescence/fizzing due to production of CO₂.

How can sodium carbonate be used as a test for carboxylic acids?

Add solid Na₂CO₃. Effervescence occurs because CO₂ is produced.

What other carbonate reagent can be used?

Aqueous NaHCO₃.

What is the key exam phrase for the carbonate test?

“Effervescence caused by production of CO₂.”

How can a carboxylic acid salt be converted back into the carboxylic acid?

Add a strong acid, e.g. HCL

What happens when HCL is added to sodium propanoate?

propanoic acid and sodium chloride formed

CH₃CH₂CO₂⁻Na⁺ + HCl → CH₃CH₂CO₂H + NaCl

Why is a strong acid added?

to protonate the carboxylate ion and form the carboxylic acid