Carbon dioxide is a colorless and odorless gas that can be detected by adding it to a solution and observing the changes in the solution. The aqueous solution of calcium hydroxide (Ca(OH)2) is used to detect the presence of carbon dioxide.

Explanation:

Calcium hydroxide (Ca(OH)2) is a white powder that is sparingly soluble in water. When calcium hydroxide is dissolved in water, it forms a solution called lime water, which is a weakly basic solution with a pH of around 12.5.

When carbon dioxide gas is bubbled through lime water, it reacts with calcium hydroxide to form calcium carbonate (CaCO3), which is insoluble in water. The reaction can be represented as follows:

Ca(OH)2 + CO2 → CaCO3 + H2O

As calcium carbonate is insoluble in water, it forms a white precipitate in the lime water, which makes the solution cloudy. The cloudiness of the lime water is a sign of the presence of carbon dioxide.

Uses:

- Lime water is used as a simple chemical test for the presence of carbon dioxide.
- It is also used in the production of calcium carbonate, which is an important industrial chemical used in the manufacture of cement, paper, plastics, and other products.
- Lime water can also be used to neutralize acidic soil in agriculture.

Conclusion:

Thus, the aqueous solution of calcium hydroxide (Ca(OH)2) is used to detect the presence of carbon dioxide by forming a white precipitate of calcium carbonate, which makes the solution cloudy.