What is lime water test for the detection of carbon dioxide class 10

The lime water test is used to detect the presence of carbon dioxide gas evolving during an experiment.

Let carbon dioxide gas is produced by the action of dilute hydrochloric acid on sodium carbonate.

 `Na_2CO_(3(aq)) + 2HCl_((aq)) →2NaCl_((aq)) + H_2O_((l)) + CO_(2(g))`

When carbon dioxide is passed through lime water (calcium hydroxide).

Lime water turns milky due to the formation of milky suspension or precipitate of calcium carbonate.

Following is the lime water test equation

`Ca(OH)_2  + CO_(2(g)) →CaCO_(3(s))  + H_2O`

If a gas produced is passed through lime and turns milky, it indicates the gas is carbon dioxide.

Note:- When excess carbon dioxide is passed through the solution, the white precipitate dissolves due to the formation of calcium hydrogen carbonate.

`CaCO_(3(s))  + H_2O_((l)) + CO_(2(g)) → Ca(HCO3)_(2(aq))`

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FAQs

1. What is the aim of the lime water test?

Ans.-  The aim of the lime water test is to find the presence of carbon dioxide gas.

2. What is the chemical formula of the white precipitate formed during the lime water test?

Ans.-  CaCO3

3. How can we find if carbon dioxide gas is present during the lime water test?

Ans.- if the solution of lime water turns milky, it shows the presence  of CO2

4. Which solution is used in the lime water test?

Ans.-  calcium hydroxidee