Calgon used as a water softner is

Options

A. `Na_(2)[Na_(4)(PO_(3))_(6)]`
B. `Na_(4)[Na_(2)(PO_(3))_(6)]`
C. `Na_(2)[Na_(4)(PO_(4))_(5)]`
D. `Na_(4)[Na_(4)(PO_(4))_(6)]`

Answer

**Solution:**

1. **Identify Calgon**: Calgon is a commercial name for a water softener. The main purpose of a water softener is to remove hardness from water, which is usually caused by the presence of calcium (Ca²⁺) and magnesium (Mg²⁺) ions.

2. **Chemical Name**: The chemical name for Calgon is sodium hexametaphosphate.

3. **Chemical Formula**: The chemical formula for sodium hexametaphosphate is Na6P6O18. However, it can also be represented in a different form: Na2Na4P6O18, which can be simplified to Na2Na4(PO3)6.

4. **Reaction with Hard Water**: When Calgon reacts with hard water, it forms a complex with the calcium ions. The reaction can be represented as:
\[ 2 \text{Na}^+ + \text{Na}_4\text{P}_6\text{O}_{18}^{2-} + \text{Ca}^{2+} \rightarrow \text{Na}_2\text{CaP}_6\text{O}_{18}^{2-} + 2 \text{Na}^+ \]
In this reaction, sodium ions (Na⁺) and calcium ions (Ca²⁺) interact with sodium hexametaphosphate, resulting in the formation of a complex that helps to soften the water.

5. **Conclusion**: Therefore, the correct answer to the question "Calgon used as a water softener is" is:
\[ \text{Na}_2\text{Na}_4\text{PO}_3\text{ whole } 6 \]