Problem 77 - A Complete Resource Book in Chemistry for JEE Main

Question

In case of auto catalysis (a) reactant catalyses (b) product catalyses (c) solvent catalyses (d) heat produced in the reaction catalyses

Step-by-Step Solution

Answer

(b) product catalyses

Step 1: Define Autocatalysis

Autocatalysis is a type of reaction where the product of the reaction acts as a catalyst for the reaction itself. This means the rate of the reaction increases as more product is formed.

Step 2: Identify the Role of Each Component

In the given options for the question: (a) Reactant is a substance that starts the reaction, not a catalyst. (b) Product is a result of the reaction and increases the reaction rate when acting as a catalyst. (c) Solvent is a medium for the reaction and does not typically act as a catalyst. (d) Heat is energy released and not a catalyst.

Step 3: Determine the Correct Option

Considering the explanation above, in autocatalysis, it is the product that acts as a catalyst to enhance the reaction rate. Therefore, option (b) is the correct answer.

Key Concepts

Reaction Kinetics

Reaction kinetics is the study of the rates at which chemical reactions occur. It helps us understand how different conditions and components affect the speed of a reaction.
In simple terms, if you think of a chemical reaction as a race, reaction kinetics is about finding out how fast the race goes and what influences the speed.
Factors that affect reaction kinetics include:

• The concentration of reactants: Higher concentration often means more collisions between molecules, thus a faster reaction.
• Temperature: Increasing the temperature usually accelerates reactions because molecules move faster and collide more often.
• Catalysts: These are substances that increase the reaction rate without being consumed in the process. They provide an alternative pathway for the reaction with a lower activation energy.
• The physical state of reactants: The surface area can affect rates; gases and liquids typically react faster than solids.

Understandably, autocatalysis—where a product of the reaction speeds up the reaction—presents a unique twist in reaction kinetics as it changes the dynamics of the reaction over time.

Catalysis

Catalysis is a fascinating phenomenon in chemistry where a substance, called a catalyst, speeds up a chemical reaction without itself being consumed.
What makes catalysis intriguing is that it only takes a small amount of catalyst to significantly increase the rate of reaction.
There are several types of catalysis:

• Homogeneous catalysis: The catalyst is in the same phase as the reactants, usually dissolved in a solution.
• Heterogeneous catalysis: The catalyst is in a different phase, often solid, and the reactants are usually gases or liquids interacting with its surface.
• Autocatalysis: Here, the interesting part is the product of the reaction acts as a catalyst. In a way, the reaction becomes self-sustaining and accelerates as more product forms.

A distinguishing feature of catalysts is that they lower the activation energy, which is the minimum energy required for the reaction to occur, hence making the process faster and more efficient.

Chemical Reactions

Chemical reactions are processes where substances, known as reactants, are transformed into different substances, called products.
During a chemical reaction, bonds between atoms in the reactants are broken and new bonds are formed to make the products. This rearrangement of atoms results in the change of properties and energy.

• Types of chemical reactions include combination, decomposition, single displacement, and double displacement.
• Exergonic reactions release energy, whereas endergonic reactions absorb energy.
• Reactions can be slow, like rusting, or fast, like an explosion.

Chemical reactions often require certain conditions to proceed, such as specific temperatures, pressures, or catalysts to help facilitate the process as seen in autocatalysis.
Understanding the factors that affect chemical reactions allows scientists and engineers to control and optimize these processes for industrial and laboratory applications.