Problem 76 - A Complete Resource Book in Chemistry for JEE Main

Question

The process, which is catalysed by one of the products, is called (a) acid base catalysis (b) negative catalysis (c) positive catalysis (d) auto catalysis

Step-by-Step Solution

Answer

The process is called auto catalysis (option d).

Step 1: Understanding Catalysis

Catalysis is a process in which the rate of a chemical reaction is increased or decreased by a substance called a catalyst. Depending on the nature of the catalyst and its interactions with the reactants or products, catalysis can be classified into different types such as positive, negative, or auto catalysis.

Step 2: Identifying Auto Catalysis

Auto catalysis occurs when one of the products of the reaction acts as a catalyst itself, enhancing the rate of the reaction. This self-catalyzing effect means the reaction speeds up as it progresses, due to the increasing concentration of the product that acts as a catalyst.

Step 3: Evaluating Options

Given the definitions: (a) acid base catalysis involves acids or bases as catalysts, (b) negative catalysis involves slowing down a reaction, (c) positive catalysis involves speeding up a reaction with an external catalyst, and (d) auto catalysis involves the catalysis by a product of the reaction itself.

Step 4: Selecting the Correct Answer

Based on the definitions and characteristics of each type of catalysis, the process described in the problem—where the reaction is catalyzed by one of its own products—is termed auto catalysis.

Key Concepts

Auto Catalysis

In chemistry, some reactions have a special twist: they seem to get faster all by themselves as they go on. This is because they are auto-catalyzed, meaning that one of the products of the reaction itself acts as a catalyst.
Imagine you're baking cookies, and somehow the cookies themselves help bake even more cookies! That's the magic of auto catalysis. Auto catalysis can be fascinating because it often shows a kind of chain reaction. As more of the product is formed, it further speeds up the reaction by acting as a catalyst.

• Increases the reaction rate without external help.
• Self-enhancing effect due to product formation.
• Can make chemical processes quicker and more efficient.

To spot an auto-catalyzed reaction, watch for any product that increases in concentration and also accelerates the reaction itself.

Chemical Reaction Kinetics

Chemical reaction kinetics studies how fast chemical reactions occur and what factors influence these speeds. In other words, it's all about understanding and measuring how changes in conditions speed up or slow down reactions. Several factors affect reaction speed:

• Concentration: Higher concentrations of reactants often lead to faster reactions.
• Temperature: Generally, increasing the temperature gives the reacting molecules more energy, leading to quicker reactions.
• Catalysts: These substances can significantly alter reaction speeds without being consumed in the process. They offer an alternative pathway with a lower activation energy.

It's important to note that in auto catalysis, as one product of the reaction acts as a catalyst, it plays a dual role in speeding up its own formation.
The study of kinetics becomes essential when shaping industrial chemical processes to ensure optimal speeds and efficiency.

Reaction Mechanisms

Reaction mechanisms describe the step-by-step sequence of elementary reactions by which overall chemical change occurs.
Understanding these steps is like unraveling the puzzle of how reactants transform into products.

• Elementary Steps: Each reaction can be broken down into simpler, single-step processes.
• Intermediates: These are short-lived species that appear in the middle of a reaction mechanism but aren't in the final product.
• Transition States: High-energy states that occur during the conversion of reactants to products.

In auto catalyzed reactions, one of the fascinating aspects is how a product can return as a catalyst in subsequent steps. By analyzing reaction mechanisms, chemists gain insights into which steps can be targeted to optimize and control the reaction effectively.