Question

When air is blown from mouth into a test - tube containing calcium hydroxide, the colour of the solution changes to ___________ , due to presence of ____________. Select one: a. milky, carbon -dioxide b. brown , water vapours c. colourless, carbon-di-oxide d. white, nitrogen

Answer 1

Here's your answer:-

on blowing air into calcium hydroxide (CaOH) solution, it reacts with the carbon dioxide in exhaled breath to form a cloudy precipitate of calcium carbonate (CaCO3) [this os the basis for limewater test for carbon dioxide]. In effect we have regenerated the original limestone.

so formula is:-

calcium hydroxide + carbon dioxide - calcium carbonate

CaOH + CO2 - CaCO3