Making carbon dioxide

Making carbon dioxide takes nothing but limestone and a dilute acid.

The reaction

Carbon dioxide (CO₂) gas can be produced by reacting calcium carbonate (CaCO₃) with dilute hydrochloric (HCl) acid.

CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂

Three products — a salt, water and the gas we want.

Figure to be added

Figure 16.5 — preparing carbon dioxide gas in the laboratory; the thistle funnel, the conical flask, the rubber bung, the dilute hydrochloric acid, the limestone, the delivery tube, the gas jar and the trough.

Compare this with the hydrogen apparatus of figure 16.2 — the set-up is the same. All that differs is what is in the flask: limestone instead of zinc.

Note carefully

Although a small amount dissolves when carbon dioxide is collected over water, that is no obstacle to collecting samples of the gas.

But since CO₂ is heavier than air, on the next page we meet a second method that suits it better.