======Limewater Test for Carbon Dioxide======


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**Alternative titles:** Test for Carbon Dioxide Gas
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====Summary====                   
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====Procedure====  
  - Prepare a test tube or small beaker containing limewater (calcium hydroxide solution).  Limewater can be made by adding pieces of calcium metal to distilled water.  
  - Bubble the suspected gas through the limewater using a delivery tube.  
  - Observe any color change in the limewater.  
  - If carbon dioxide is present, the limewater will turn cloudy or milky.



====Links==== 
Testing for CO2 (Carbon dioxide) with Limewater - Wayne Breslyn (Dr. B.): 
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Limewater Test for Carbon Dioxide. - Primrose Kitten Academy: 
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📄 Tests for gases - BBC Bitesize: [[https://www.bbc.co.uk/bitesize/guides/z6dtgwx/revision/1]]\\

====Variations====
  * Use a straw to gently blow into limewater to demonstrate exhaled carbon dioxide.  
  * Compare with bubbling oxygen, nitrogen, or hydrogen through limewater to confirm no change occurs.



====Safety Precautions====
  * Wear safety glasses to protect eyes from splashes.  
  * Do not inhale directly from the gas delivery tube.  
  * Avoid prolonged blowing into limewater, as it may increase risk of contamination or ingestion.  
  * Handle calcium hydroxide carefully, as it is mildly caustic.




====Questions to Consider====
  * What chemical forms when carbon dioxide reacts with limewater? (Calcium carbonate.)  
  * Why does the limewater eventually clear if excess carbon dioxide is added? (Because calcium carbonate reacts with more carbon dioxide and water to form soluble calcium hydrogencarbonate.)  
  * Why is this test unique to carbon dioxide? (Other common gases do not react with limewater to produce a cloudy precipitate.)