Question

PROCEDURE: CARBON DIOXYDE

Take one of the lime water test tube, shake and observe.

Was there any detectible amount of carbon dioxide in the air? Can you give me any idea above what it is expected? Set it aside.

Pour another 5 mL of lime water to one of the test tubes that has the collected carbon dioxide, put the stopper back on, shake and compare with the one was shaken in the air.

Answer 1

When lime water[Ca(OH)2] comes in contact with CO2, it turns milky due to the formation of CaCO3(s).

Ca(OH)₂(aq) + CO₂(g) ----- > CaCO₃(s) + H₂O(l)

Since normal air contans very small amount of CO2, the milky color doesn't appear suddenly when we expose lime water to air. How ever if we keep the lime water in air for a long time it will gradually turm milky.

When we pour lime water to a test tube containing already collected CO2, the concentration of CO2 in air is very high in comparisn to normal air. Hence the intensity of milky color produced here is very high in comparison to the color produced in normal air.