Question
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What happens when excess co2 is passed through lime water?

Verified Answer

When excess carbon dioxide (CO₂) is passed through lime water (calcium hydroxide solution), the lime water first turns milky due to the formation of calcium carbonate (CaCO₃). If more CO₂ is passed, the milkiness disappears because calcium carbonate reacts with excess CO₂ and water to form soluble calcium bicarbonate [Ca(HCO₃)₂].

Chemical Reactions:

  • Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

  • CaCO₃ + CO₂ + H₂O → Ca(HCO₃)₂

This reaction is commonly used to test the presence of carbon dioxide gas.