The formula of Calgon is :

Options

A. `Na_(6)P_(6)O_(18)`
B. `Na_(5)P_(5)O_(18)`
C. `Na_(4)P_(4)O_(18)`
D. `Na_(2)MP_(6)O_(18)`

Answer

To find the formula of Calgon, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Calgon**: Calgon is a chemical compound used to soften hard water. Hard water contains high levels of calcium and magnesium ions, which can cause scaling and reduce the effectiveness of soaps.

2. **Identifying the Components of Hard Water**: The impurities in hard water typically include calcium chloride (CaCl₂), magnesium chloride (MgCl₂), calcium sulfate (CaSO₄), and magnesium sulfate (MgSO₄).

3. **Reaction with Calgon**: Calgon reacts with these impurities to form soluble complexes, thus removing calcium and magnesium ions from the water.

4. **Chemical Formula of Calgon**: The chemical formula for Calgon is derived from its composition. The formula is Na₂Na₄(PO₃)₆, which can be simplified to Na₆P₆O₁₈.

5. **Counting Atoms in the Formula**:
- Sodium (Na): There are 6 sodium atoms.
- Phosphorus (P): There are 6 phosphorus atoms.
- Oxygen (O): There are 18 oxygen atoms.

6. **Final Formula**: Therefore, the complete and correct formula of Calgon is Na₆P₆O₁₈.

7. **Selecting the Correct Option**: Among the given options, the correct formula is Na₆P₆O₁₈.

### Conclusion:
The formula of Calgon is **Na₆P₆O₁₈**.

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