Preparation of Carbon Dioxide: quick revision, 10 bites

Acid + Carbonate = Carbon Dioxide

One reaction unlocks CO₂ in the lab.

In the laboratory, carbon dioxide is prepared by reacting a **carbonate** with a **dilute acid**. The most common pair is marble chips (calcium carbonate) and dilute hydrochloric acid.

Takeaway. Any metal carbonate + dilute acid releases carbon dioxide gas.

Key Terms You Must Know

Master the vocabulary before the reaction.

Takeaway. Knowing these four terms makes the whole preparation easy to follow.

How to Prepare CO₂ in the Lab

Five steps from chips to collected gas.

Takeaway. Marble chips + dilute HCl, then collect downward because CO₂ is denser than air.

Why Collect CO₂ by Downward Delivery?

Denser than air — so it sinks.

Takeaway. Denser-than-air gases are collected by downward delivery, not over water.

Testing the Gas: The Limewater Test

Cloudy limewater proves CO₂ is present.

Takeaway. Limewater turning milky is the confirmatory test for carbon dioxide.

Don't Use Sulphuric Acid

Wrong acid stops the reaction cold.

Takeaway. Dilute HCl works; dilute H₂SO₄ blocks the reaction with an insoluble coat.

CO₂ in Everyday Life

From fizzy drinks to fire extinguishers.

Takeaway. The same gas prepared in the lab powers drinks, baking and fire safety.

Remember the Collection Method

Heavy gas? Send it down.

Think: **"Heavy gases go down, light gases go up."** Carbon dioxide is heavier than air, so it is collected by **downward delivery**.

Takeaway. Denser gas → downward delivery; lighter gas → upward delivery.

Exam Points You Must Write

Score full marks on this question.

Takeaway. Equation + method + reason + test = full marks.

CO₂ Is Not Always a Gas

Freeze it and it becomes 'dry ice'.

When carbon dioxide is cooled and compressed, it turns directly into a **solid called dry ice** without becoming a liquid at normal pressure. Dry ice is used for refrigeration and fog effects.

Takeaway. Solid CO₂ (dry ice) sublimes directly to gas — no liquid stage at normal pressure.