Does calcium hydroxide react with carbon dioxide?
Yes, **calcium hydroxide (Ca(OH)₂)*, commonly known as limewater when in solution, readily reacts with carbon dioxide (CO₂)**.
This reaction is a fundamental chemical process with significant practical applications, particularly as a common test for the presence of carbon dioxide.
As confirmed by the provided reference, when carbon dioxide is introduced into a solution of calcium hydroxide, a distinct chemical reaction takes place:
"Carbon dioxide reacts with limewater (a solution of calcium hydroxide, Ca(OH)₂), to form a white precipitate. (appears milky) of calcium carbonate, CaCO₃."
This interaction results in the formation of calcium carbonate (CaCO₃), which is insoluble in water. Its appearance as a white precipitate causes the limewater to turn visibly milky or cloudy, confirming the reaction. Water is also produced as a byproduct.
Chemical Equation
The chemical transformation can be precisely represented by the following balanced equation:
Ca(OH)₂(aq) + CO₂(g) → CaCO₃(s) + H₂O(l)
Where:
Ca(OH)₂: Calcium Hydroxide (in aqueous solution, i.e., limewater)CO₂: Carbon Dioxide (gas)CaCO₃: Calcium Carbonate (solid precipitate)H₂O: Water (liquid)
Summary of Reactants and Products
| Component | Chemical Formula | State (in reaction) | Role |
|---|---|---|---|
| Calcium Hydroxide | Ca(OH)₂ | Aqueous (limewater) | Reactant |
| Carbon Dioxide | CO₂ | Gaseous | Reactant |
| Calcium Carbonate | CaCO₃ | Solid (Precipitate) | Product |
| Water | H₂O | Liquid | Byproduct |
Practical Applications and Insights
The reaction between calcium hydroxide and carbon dioxide is not merely an academic concept; it underpins several important real-world applications:
- Laboratory Test for Carbon Dioxide: This reaction is the definitive qualitative test for carbon dioxide gas. If a gas passed through limewater causes it to turn milky, the presence of CO₂ is confirmed.
- Carbonation of Concrete and Mortar: Calcium hydroxide is a key component in cement, which forms concrete and mortar. Over time, atmospheric carbon dioxide reacts with the calcium hydroxide in hardened concrete to form calcium carbonate. This process, known as carbonation, contributes to the long-term strength and durability of concrete but can also affect its pH and potentially lead to rebar corrosion if left unchecked.
- Air Purification and Scrubber Systems: In enclosed environments such as submarines or spacecraft, substances like calcium hydroxide (or related compounds) can be used in CO₂ scrubbers to remove excess carbon dioxide from the air, ensuring a breathable atmosphere for occupants.
This direct and visible chemical interaction highlights calcium hydroxide's role as a base and its ability to react with acidic gases like carbon dioxide, leading to the formation of a stable carbonate salt.
