The desiccants used for absorbing water during Liebig's method for estimation of carbon and hydrogen are

Options

A. `CaCl_(2)`
B. `Na_(2)SO_(4)`
C. `MgSO_(4).7H_(2)O`
D. `Mg(ClO_(4))_(2)`

Explanation

To answer the question regarding the desiccants used for absorbing water during Liebig's method for the estimation of carbon and hydrogen, we will analyze the provided options step by step.

### Step-by-Step Solution:

1. **Understanding the Context**:
- Liebig's method is a classical technique used for the estimation of carbon and hydrogen in organic compounds.
- A desiccant is a substance that absorbs moisture from the air, which is crucial in this method to ensure accurate measurements.

2. **Analyzing the Options**:
- **Option A: Calcium Chloride (CaCl₂)**
- Calcium chloride is a well-known desiccant and is anhydrous (without water).
- It belongs to the second group of the periodic table (alkaline earth metals) and has high hydration energy, making it effective for moisture absorption.

- **Option B: Anhydrous Sodium Sulfate (Na₂SO₄)**
- Sodium sulfate is typically used as a drying agent, but it belongs to the first group of metals (alkali metals).
- Although anhydrous, it is not as effective as the second group metals for this specific application.

- **Option C: Magnesium Sulfate Heptahydrate (MgSO₄·7H₂O)**
- Magnesium sulfate is also a second group metal salt, but in this case, it is in its hydrated form (heptahydrate).
- While it can absorb moisture, it is not in the anhydrous form required for the desiccant role in Liebig's method.

- **Option D: Magnesium Chloride Dihydrate (MgCl₂·2H₂O)**
- This compound is also hydrated and not suitable for use as a desiccant in this context.

3. **Conclusion**:
- The effective desiccants from the options provided are:
- **Option A: Calcium Chloride (CaCl₂)** - Suitable as it is anhydrous and belongs to the second group.
- **Option C: Magnesium Sulfate (though not in anhydrous form, it can still absorb moisture)** - However, since it is not anhydrous, it is not ideal.
- Therefore, the correct answer is **Option A** (Calcium Chloride) is the primary desiccant used in Liebig's method.

### Final Answer:
The desiccants used for absorbing water during Liebig's method for estimation of carbon and hydrogen are **Calcium Chloride (CaCl₂)**.