Which of the following statements about the zeolites is false?

Options

A. They are used as cation exchangers
B. Some of the `SiO_(4)^(4-)` units are replaced by `AIO_(4)^(5-)` and `AIO_(6)^(9-)` ions in zeolite.
C. They have open structure which enables them to take up small molecules.
D. Zeolites are aluminosilicates having three dimensional structures.

Explanation

To determine which statement about zeolites is false, we will analyze each option provided in the question.

### Step 1: Analyze Option 1
**Statement:** Zeolites are used as cation exchangers.
**Explanation:** Zeolites are indeed known for their ability to act as ion exchangers. They can exchange cations in solution, which is a key property used in applications like water softening. For example, sodium zeolites can exchange sodium ions for calcium ions in hard water.
**Conclusion:** This statement is **true**.

### Step 2: Analyze Option 2
**Statement:** Some of the SiO4 negative units are replaced by AlO4F-.
**Explanation:** This statement is misleading. In zeolites, some of the SiO4 units can be replaced by AlO4 units, but the mention of AlO4F- is incorrect. The correct replacement involves AlO4 units, which are negatively charged due to the presence of aluminum.
**Conclusion:** This statement is **false**.

### Step 3: Analyze Option 3
**Statement:** Zeolites have an open structure that enables them to take up small molecules.
**Explanation:** Zeolites possess a porous structure that allows them to trap and adsorb small molecules such as water, ammonia, and carbon dioxide. This property is essential for their applications in catalysis and adsorption.
**Conclusion:** This statement is **true**.

### Step 4: Analyze Option 4
**Statement:** Zeolites are aluminosilicates having three-dimensional structures.
**Explanation:** This statement is accurate. Zeolites are indeed aluminosilicates, and they have a three-dimensional framework structure. The presence of aluminum in the structure creates a negative charge that must be balanced by cations.
**Conclusion:** This statement is **true**.

### Final Conclusion
Based on the analysis, the false statement about zeolites is **Option 2**: "Some of the SiO4 negative units are replaced by AlO4F-."

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