Which of the following will be the most hydrated salt ?
(1) NaCl (2) `MgCl_2` (3) `AlCl_3` (4) `SiCl_4`

Explanation

To determine which of the given salts will be the most hydrated, we need to analyze the properties of each salt in relation to their ability to form hydrates. Let's break down the steps:

### Step 1: Identify the nature of the salts
The salts provided are:
1. NaCl (Sodium chloride)
2. MgCl₂ (Magnesium chloride)
3. AlCl₃ (Aluminum chloride)
4. SiCl₄ (Silicon tetrachloride)

### Step 2: Understand the concept of hydration
Hydration refers to the process where water molecules surround and interact with solute ions. The ability of a salt to form hydrates depends on the balance between lattice energy (the energy required to separate the ions in the solid) and hydration energy (the energy released when water molecules surround the ions).

### Step 3: Analyze the salts
- **NaCl**: Sodium chloride is an ionic compound but does not have a very high hydration capacity compared to other salts.
- **MgCl₂**: Magnesium chloride is known for its ability to form hydrates. It has a relatively high charge density due to the divalent magnesium ion (Mg²⁺), which leads to strong interactions with water molecules.
- **AlCl₃**: Aluminum chloride can form hydrates, but it tends to form covalent bonds in the anhydrous state and may not be as hydrated as MgCl₂.
- **SiCl₄**: Silicon tetrachloride is a covalent compound and does not typically form hydrates.

### Step 4: Compare hydration capacities
Among the salts:
- **MgCl₂** is known to form several hydrates, such as MgCl₂·6H₂O (hexahydrate), which indicates a strong ability to incorporate water molecules.
- **NaCl** and **AlCl₃** do not form hydrates as readily as MgCl₂.
- **SiCl₄** does not form hydrates at all.

### Conclusion
Based on the analysis, **MgCl₂** (Magnesium chloride) will be the most hydrated salt among the options provided.

### Final Answer
The most hydrated salt is **(2) MgCl₂**.

---