Question

Which of the following statements are correct about solid catalyst? (a) Catalyst is required in large quantities to catalyse reactions. (b) Catalytic activity of a solid catalyst does not depend upon the strength of chemisorptions (c) Same reactants may give different product by using different catalysts. (d) Catalyst does not change \(\Delta \mathrm{H}\) of reaction.

Short answer

Statements (c) and (d) are correct.

Step-by-step solution

Evaluate statement (a)

Statement (a) claims that a catalyst is required in large quantities to catalyze reactions. This is incorrect because catalysts are typically required only in small amounts since they are not consumed in the reaction and can be reused multiple times.

Evaluate statement (b)

Statement (b) suggests that the catalytic activity of a solid catalyst does not depend on the strength of chemisorption. This is false because the effectiveness of a solid catalyst often depends on the right amount of chemisorption, which needs to be strong enough to activate the reactants, but not so strong that the products cannot desorb.

Evaluate statement (c)

Statement (c) claims that the same reactants may give different products when using different catalysts. This is true, as different catalysts can provide different pathways for the reaction, often leading to different products.

Evaluate statement (d)

Statement (d) asserts that a catalyst does not change the enthalpy change (94H) of the reaction. This is correct because a catalyst speeds up the reaction by lowering the activation energy, not by altering the thermodynamics of the reaction.

Key concepts

Catalyst Quantity

Did you know that when using a solid catalyst, you generally don't need much of it? That's right! Catalysts are brilliantly efficient because they don't get consumed during the reaction process.
Moreover, they can be used over and over again. This means you only need a small amount to effectively catalyze a reaction.

• Efficiency: Catalysts can work on large amounts of reactants while staying unchanged.
• Reusability: They can be reused several times without losing their effectiveness.

This efficiency is a major reason why catalysts are so valued in chemical processes, especially industrial ones where cost and material efficiency are key.

Chemisorption

Chemisorption plays a crucial role in the efficacy of solid catalysts. It's a type of adsorption where a chemical reaction occurs between the surface and the adsorbate.
But, here's the catch: for a catalyst to work optimally, the chemisorption must be just right. If it's too weak, the reactants won't stick well enough to react, but if it's too strong, the products might stick and not leave the surface.

• Balance: Optimal strength allows reactants to be activated and products to detach easily.
• Activation: A proper chemisorption strength ensures that the reactants are activated for the reaction.

Thus, understanding this balance is vital for designing effective catalysts.

Catalyst Pathways

The magic of catalysts lies in their ability to offer different pathways for the same reaction.
What's amazing is that using different catalysts with the same reactants can lead to entirely different products. This is because catalysts can alter the reaction pathway by changing the mechanism of the reaction.

• Pathway Variation: Different catalysts can open up alternate pathways for a reaction.
• Product Selectivity: The pathway chosen can lead to distinct products from the same reactants.

This variability makes catalysts incredibly versatile tools in chemistry, as they allow for tailored reactions to get the desired end-products.

Reaction Enthalpy

A catalyst doesn't alter the enthalpy change (\( \Delta H \)) of a reaction.
This might sound surprising, but catalysts work by only changing the rate of the reaction and not the energy balance. The enthalpy change is fundamentally a property of the reactants and products.

• Energy Balance: The overall energy content remains the same with or without a catalyst.
• Rate of Reaction: Catalysts only speed up the rate by lowering the activation energy required.

So, while a catalyst makes reactions faster, it doesn't play with the heat or energy involved with the reaction.