When zeolite which is hydrated sodium aluminium silicate is treated with hard water, the sodium ions are exchanged with which of the following ion (S)?

Options

A. `H^(+)` ion
B. `Mg^(2+)` ions
C. `Ca^(2+)` ions
D. `SO_(4)^(2-)` ions

Explanation

To solve the question, we need to understand the process of ion exchange that occurs when zeolite interacts with hard water. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand the Composition of Zeolite
Zeolite is described as hydrated sodium aluminium silicate. Its chemical formula can be represented as Na2AlSiO3·XH2O, where Na+ ions are the sodium ions present in the structure.

**Hint for Step 1:** Remember that zeolite contains sodium ions that can be exchanged during the ion exchange process.

### Step 2: Identify the Problem with Hard Water
Hard water contains high concentrations of certain cations, primarily calcium (Ca²⁺) and magnesium (Mg²⁺) ions. These ions are responsible for the hardness of the water.

**Hint for Step 2:** Recall that hard water is characterized by the presence of calcium and magnesium ions.

### Step 3: Understand the Ion Exchange Process
When zeolite is treated with hard water, the sodium ions (Na⁺) in the zeolite are exchanged for the cations present in the hard water. The zeolite has a unique property of exchanging cations, which allows it to soften hard water.

**Hint for Step 3:** Focus on the concept of cation exchange, where sodium ions are replaced by other cations from the water.

### Step 4: Identify the Cations Being Replaced
In the case of hard water, the cations that are exchanged with sodium ions are primarily calcium (Ca²⁺) and magnesium (Mg²⁺) ions. Therefore, when zeolite is treated with hard water, the sodium ions are exchanged for these cations.

**Hint for Step 4:** Look for the specific ions that are typically responsible for water hardness.

### Step 5: Conclusion
Thus, when zeolite is treated with hard water, the sodium ions are exchanged with calcium (Ca²⁺) and magnesium (Mg²⁺) ions.

**Final Answer:** The sodium ions are exchanged with Ca²⁺ and Mg²⁺ ions.