Question

Why lime water changes the colour when carbondioxide is blown into the test tube?

Answer 1

Answer:

The reactants and products in this case, along with their formulae-

Lime Water : $\bold{Ca(OH)_2}$

Carbon Dioxide : $\bold{CO_2}$

Calcium Carbonate: $\bold{CaCO_3}$

Water : $\bold{H_2O}$

Let's look at the reaction now!

Lime Water + Carbon Dioxide --------> Calcium Carbonate + Water

OR

$\bold{Ca(OH)_2}$ + $\bold{CO_2}$ --------> $\bold{CaCO_3}$ + $\bold{H_2O}$

$\bold{CaCO_3}$ is actually the white precipitate which makes the lime water milky. On addition of more carbon dioxide to this solution, the solution becomes colourless as the precipitate then becomes soluble as it is changed to calcium bicarbonate, having the chemical formula $\bold{Ca(HCO_3)_2}$

Answer 2

Answer:

The reactants and products in this case, along with their formulae-

Lime Water : Ca(OH)2

Carbon Dioxide : CO2

Calcium Carbonate: CaCO3

Water : H2O

Let's look at the reaction now!

Lime Water + Carbon Dioxide --------> Calcium Carbonate + Water

OR

Ca(OH)2 + CO2---------->CaCO3+H2O

CaCO3 is actually the white precipitate which makes the lime water milky. On addition of more carbon dioxide to this solution, the solution becomes colourless as the precipitate then becomes soluble as it is changed to calcium bicarbonate, having the chemical formula Ca(HCO3)2