1. Limewater Test:
* Procedure: Bubble the gas through a solution of calcium hydroxide (limewater).
* Observation: If carbon dioxide is present, the limewater will turn milky white due to the formation of calcium carbonate (CaCO3), an insoluble white precipitate.
* Chemical Equation:
CO2(g) + Ca(OH)2(aq) → CaCO3(s) + H2O(l)
2. Bromothymol Blue Indicator Test:
* Procedure: Bubble the gas through a solution of bromothymol blue indicator (which is blue in basic solutions).
* Observation: Carbon dioxide is acidic, so it will react with water to form carbonic acid. This will lower the pH of the solution, causing the bromothymol blue to change color from blue to yellow.
* Chemical Equation:
CO2(g) + H2O(l) ⇌ H2CO3(aq)
Additional Notes:
* Other Gases: Some other gases can also cause a slight clouding in limewater, but not as intense as carbon dioxide. It's always good to compare the reaction with a known sample of carbon dioxide.
* Safety: Always handle chemicals with care, wear appropriate safety gear, and work in a well-ventilated area.
These tests are reliable and simple ways to confirm the presence of carbon dioxide.
