Question

In the following question two statements Assertion (A) and Reason (R) are given Mark. a. If \(\mathrm{A}\) and \(\mathrm{R}\) both are correct and \(\mathrm{R}\) is the correct explanation of \(\mathrm{A}\); b. If \(A\) and \(R\) both are correct but \(R\) is not the correct explanation of \(\mathrm{A}\); c. \(\mathrm{A}\) is true but \(\mathrm{R}\) is false; d. \(\mathrm{A}\) is false but \(\mathrm{R}\) is true, e. \(\mathrm{A}\) and \(\mathrm{R}\) both are false. (A): A catalyst enhances the rate of reaction. ( \(\mathbf{R}\) ): The energy of activation of the reaction is lowered in presence of a catalyst.

Short answer

Both A and R are correct and R explains A.

Step-by-step solution

Understanding Assertion (A)

The assertion (A) states that a catalyst enhances the rate of a chemical reaction. A catalyst is a substance that increases the rate of a reaction by providing an alternative pathway with a lower activation energy without being consumed in the reaction.

Understanding Reason (R)

The reason (R) states that the energy of activation of the reaction is lowered in the presence of a catalyst. This is a correct statement, as catalysts work by reducing the activation energy needed for a reaction to proceed, thus increasing the reaction rate.

Evaluating the Relationship

Both the assertion (A) and reason (R) are true. Moreover, reason (R) provides the correct mechanism for why a catalyst enhances the rate of reaction, since the reduction in activation energy allows more reactant molecules to have enough energy to react.

Selecting the Correct Option

Since both (A) and (R) are correct, and (R) is the correct explanation of (A), the appropriate choice is option (a): 'A is correct, and R is the correct explanation of A.'

Key concepts

Activation Energy

Activation energy is a fundamental concept in understanding chemical reactions. In simple terms, it's the energy barrier that reactants must overcome for a reaction to occur. Think of it as the initial "hill" reactants need to get over before turning into products. This energy is necessary to break bonds in reactants and form new ones in products.

Every reaction has its own specific activation energy, determined by the nature of the reacting substances and the conditions of the reaction. Higher activation energies mean that fewer molecules have enough energy to react at a given time, leading to slower reaction rates. Conversely, reactions with lower activation energies tend to occur more rapidly, as more molecules can easily acquire the necessary energy.

Understanding activation energy helps in predicting how modifications, like the addition of a catalyst, can influence the rate of a chemical reaction.

Reaction Rate Enhancement

The rate of a chemical reaction is a key factor in understanding how quickly products form from reactants. Enhancing the reaction rate means making the process run faster. But how is this achieved? One common method is by using catalysts.

Catalysts work by offering an alternative pathway for the reaction, which typically has a lower activation energy compared to the uncatalyzed pathway. This allows more reactant molecules to have the necessary energy to overcome the energy barrier, thereby speeding up the reaction.

• By lowering the activation energy.
• Increasing the number of successful collisions between reactant molecules.
• Allowing for more consistent and faster production output in industrial settings.

Through these mechanisms, catalysts accelerate chemical reactions without undergoing permanent change themselves, contributing significantly to their practical applications.

Alternative Reaction Pathway

Catalysts function by providing an alternative reaction pathway that requires lower activation energy. Imagine if your path across a mountain had a shortcut that was less steep; that's what a catalyst does for a chemical reaction.

This alternative pathway typically involves intermediate states or steps that are more favorable energetically. These intermediates require less energy to form compared to the direct conversion of reactants to products. As a result, the overall energy requirement for the reaction drops, allowing more molecules to participate in the reaction at any given time.

A key point to understand is that this alternative pathway does not alter the final products or reactants but merely changes the route and energy profile they take to reach the end of the reaction. Consequently, catalysts enable reactions to occur under conditions that might otherwise be impractical, especially in terms of time or energy requirements.