MYP 8 Science - Chemistry

MYP 8.5.7: Reaction between acids and limestone


In the previous section limestone was seen to decompose when heated. This is called thermal decomposition.

CaCO3(s) CaO(s) + CO2(g)

Student activity

The reaction between limewater and carbon dioxide

Prepare a carbon dioxide generator by connecting a rubber tube, terminating in a glass tube, to the side-arm of a side-arm test tube.

Here are a few safety notes.

Place a few marble chips into the side-arm tube and add about 20cm3 of dilute hydrochloric acid.

Place a bung into the side arm tube and using the terminating glass tube, pass the gas through a sample of limewater for a few seconds. Observe.

Allow the carbon dioxide gas to pass through the limewater for at least 1 minute. Observe.


Use of a side-arm tube in a gas generator assembly

Teaching notes

The precipitate formed by the reaction between carbon dioxide and limewater, calcium carbonate, redissolves with excess carbon dioxide due to the formation of calcium hydrogencarbonate (aq).

CaCO3(s) + CO2(g) + H2O(l) Ca(HCO3)2(aq)



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