Shape selective catalyst are so called because of :

Options

A. The shape of the catalysts
B. The specificity of the catalysts
C. The size of the pores of the catalysts which can trap only selective molecules
D. Their use for only some selected reactions

Answer

**Step-by-Step Solution:**

1. **Understanding Catalysts:**
- Catalysts are substances that increase the rate of a chemical reaction without being consumed in the process. They provide an alternative reaction pathway with a lower activation energy.

2. **Defining Shape Selective Catalysts:**
- Shape selective catalysts are a specific type of catalyst that selectively allow certain reactant molecules to enter their pores based on the size and shape of those molecules.

3. **Characteristics of Shape Selective Catalysts:**
- The key feature of shape selective catalysts is their pore structure, which is designed to trap only molecules that fit within a specific size range. This selectivity is crucial for ensuring that only desired reactions occur.

4. **Example of Shape Selective Catalysts:**
- A common example of shape selective catalysts is zeolites. Zeolites are aluminosilicate minerals that have a porous structure. Their pore sizes typically range from 260 picometers to 740 picometers.

5. **Mechanism of Action:**
- Zeolites can selectively adsorb and react with molecules whose sizes fall within the specified pore size range. Molecules larger than the pore size cannot enter, thus preventing undesired reactions and ensuring that only specific molecules are processed.

6. **Conclusion:**
- Therefore, shape selective catalysts are so called because of the size of the pores of the catalyst, which can trap only selective molecules. This characteristic allows them to be used in specific reactions where size selectivity is essential.

**Final Answer:**
Shape selective catalysts are so called because of the size of the pores of the catalyst which can trap only selective molecules.

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