Hello, I'm Dr. Emily, a chemist with a specialization in inorganic chemistry. I have over 15 years of experience researching and teaching about the fascinating interactions between chemical compounds. It's always exciting to delve into the reactions that shape our world, especially when it comes to everyday phenomena like the change in lime water with the introduction of carbon dioxide.

Let's explore the reason why lime water, which is a **saturated solution of calcium hydroxide (Ca(OH)2)**, turns cloudy when exposed to carbon dioxide (CO2) and then clears again when excess carbon dioxide is added.

The key to understanding this change lies in the chemical reactions occurring between the calcium hydroxide and carbon dioxide.


1. Initial Reaction: When carbon dioxide is bubbled into lime water, it reacts with the calcium hydroxide to form calcium carbonate (CaCO3), a white, insoluble solid. This reaction is represented by the following equation:

```
Ca(OH)2 (aq) + CO2 (g) → CaCO3 (s) + H2O (l)
```

This insoluble calcium carbonate is what causes the lime water to turn cloudy. The solution becomes milky white due to the formation of these fine, suspended particles of calcium carbonate.


2. Excess Carbon Dioxide: If you continue to bubble in carbon dioxide, the solution will eventually become clear again. This happens because the excess CO2 reacts with the calcium carbonate to form calcium hydrogencarbonate (Ca(HCO3)2), which is soluble in water. This reaction can be expressed as:

```
CaCO3 (s) + CO2 (g) + H2O (l) → Ca(HCO3)2 (aq)
```

The soluble calcium hydrogencarbonate dissolves in the water, removing the suspended calcium carbonate particles and making the solution clear again.

In summary:

- Lime water turns cloudy when exposed to carbon dioxide due to the formation of insoluble calcium carbonate.
- With the addition of excess carbon dioxide, the calcium carbonate reacts further to form soluble calcium hydrogencarbonate, causing the solution to become clear again.

This process demonstrates a fascinating interplay of chemical reactions and solubility. It highlights the dynamic nature of chemical systems and the influence of reactants' concentrations on the formation of different products.

Let me know if you have any further questions about this fascinating chemical reaction or other chemistry concepts! I am always happy to share my knowledge and help you understand the world around us.
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When carbon dioxide is passed through lime water it turns milky due to the formation of water insoluble precipitate CaCO3. Still if excess of CO2 is passed it forms water soluble Calcium bicarbonate . Thus the solution remains clear.read more >>