2KOH (aq) + CO₂ (g) → K₂CO₃ (aq) + H₂O (l)
Here's how it works:
1. Reaction: When carbon dioxide gas comes into contact with an aqueous solution of potassium hydroxide, it reacts to form potassium carbonate (K₂CO₃) and water (H₂O).
2. Visual Change: This reaction causes a decrease in the concentration of the KOH solution, which can be visually observed in a few ways:
* Limewater: If you use a solution of calcium hydroxide (limewater) instead of KOH, the reaction produces a white precipitate of calcium carbonate (CaCO₃). This is a classic test for CO₂.
* Color Change with Indicator: You can use a pH indicator that changes color in the presence of a base. As the KOH reacts with CO₂, the solution becomes less basic, and the indicator will change color accordingly.
3. Confirmation: The formation of potassium carbonate confirms the presence of CO₂.
In Summary:
The reaction between potassium hydroxide and carbon dioxide is a chemical reaction that produces a visual change, allowing you to detect the presence of carbon dioxide.
