What is the role of CaO in sodalime ?

Explanation

**Step-by-Step Solution:**

1. **Understanding Soda Lime Composition:**
- Soda lime is a mixture of sodium hydroxide (NaOH) and calcium oxide (CaO).
- The typical ratio used is three parts of NaOH to one part of CaO.

2. **Identifying the Properties of Sodium Hydroxide:**
- Sodium hydroxide is known to be hygroscopic, meaning it has a tendency to absorb moisture from the air.
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