Testing for Carbonate Ions

What is the formula of the carbonate ion?

CO₃²⁻.

How can carbonate ions be identified?

Add a dilute acid and test any gas produced with limewater.

What gas is produced when carbonate ions react with acid?

Carbon dioxide.

What happens to limewater when carbon dioxide is bubbled through it?

It turns cloudy or milky.

What is the general word equation for an acid reacting with a carbonate?

Acid + carbonate → salt + water + carbon dioxide.

What is the ionic equation for carbonate ions reacting with acid?

CO₃²⁻ + 2H⁺ → CO₂ + H₂O.

Why does adding acid to a carbonate cause fizzing?

Carbon dioxide gas is released.

Why is bubbling the gas through limewater useful?

It provides evidence that the gas is carbon dioxide.

Why is fizzing alone insufficient to confirm carbonate ions?

Other reactions may also produce gases.

What observation confirms a positive carbonate test?

Effervescence followed by limewater turning cloudy.

What is a common mistake in carbonate tests?

Saying the gas is oxygen rather than carbon dioxide.