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 does not alter the heat of reaction. (R): Catalyst increases the rate of reaction.

Short answer

Option b: A and R both are correct, but R is not the explanation of A.

Step-by-step solution

Identify the Assertion and Reason

First, we will identify both the Assertion (A) and the Reason (R) from the question. - The Assertion (A) is: "A catalyst does not alter the heat of reaction." - The Reason (R) is: "Catalyst increases the rate of reaction."

Assess the Truth of the Assertion

Examine the Assertion: A catalyst speeds up a reaction without being consumed, and it does not alter the heat (enthalpy) of the reaction. Thus, the Assertion (A) "A catalyst does not alter the heat of reaction" is true.

Assess the Truth of the Reason

Examine the Reason. A catalyst provides an alternative pathway with a lower activation energy, increasing the reaction rate. Thus, the Reason (R) "Catalyst increases the rate of reaction" is true.

Determine the Relationship Between A and R

Now we need to decide if the Reason (R) explains why the Assertion (A) is true. A catalyst not altering the heat of reaction (A) is a different concept than increasing the rate of reaction (R); they describe different aspects of a catalyst's effect.

Choose the Correct Explanation Option

Based on the truth values and explanations above, both Assertion (A) and Reason (R) are correct. However, R does not explain A. Thus, the correct option is **b**: A and R both are correct but R is not the correct explanation of A.

Key concepts

Catalyst Effect

A catalyst is a fascinating substance often used in chemistry to speed up reactions. It works without being consumed in the process. The magic behind a catalyst lies in its ability to provide a different path for the reaction to occur.
This path requires less energy, making it faster and more efficient.

• A catalyst lowers the activation energy.
• It is not used up in the reaction, so a small amount can affect a large reaction.

By changing the pathway, the catalyst can have a significant effect on the reaction rate. However, it does not alter the starting or ending substances themselves. It stays intact throughout the reaction, ready to work again.

Reaction Rate

The rate of a reaction tells us how fast it happens. When we talk about increasing the reaction rate, we're essentially talking about speeding up the process.
A catalyst can greatly enhance this by lowering the energy needed for the reaction to proceed. Think of it as removing hurdles in a race—making it easier for the reactants to turn into products.

• Faster reactions can be critical in industrial processes, where time is money.
• Catalysts offer a way to safely increase rates without altering the reaction's final balance.

Understanding how to adjust reaction rates is essential in scientific and industrial settings to optimize reactions and achieve desired results quickly.

Heat of Reaction

The heat of reaction, also known as the enthalpy change, is the amount of heat absorbed or released during a chemical reaction. A catalyst plays no part in altering this value.
This is because while a catalyst speeds up the reaction, it does not change the nature of the outcomes. The enthalpy remains constant, regardless of how fast the reaction occurs.
So whether it happens in seconds or days, the amount of heat involved stays the same. This makes catalysts incredibly efficient as they allow processes to happen quicker without needing extra heat or energy adjustments.

Enthalpy

Enthalpy is a term used to describe the total heat content of a system. In chemical reactions, we often look at how this changes as reactants form products.
One of the significant features of enthalpy is that it remains unchanged whether a catalyst is present or not. This concept is crucial because it assures that catalysts are tools to speed up reactions without altering energy conservation.

• Enthalpy changes depend on the nature of the reactants and products, not on how fast they react.
• Understanding enthalpy helps in predicting the heat exchange in various reactions.

By focusing on the science of enthalpy, chemists can better understand how reactions conserve energy while maximizing efficiency.

Activation Energy

Activation energy is the minimum energy required for a reaction to take place. It acts as a barrier that reactants need to overcome to transform into products.
A catalyst lowers this barrier, making it easier for the reaction to occur. Imagine a wall; a high wall is difficult to climb, but if you lower it, it becomes much easier to get over.

• Lower activation energy means faster reactions.
• Catalysts are widely used to reduce the activation energy in both laboratory and industrial settings.

By understanding activation energy, scientists can develop methods to speed up reactions without applying external heat, enhancing both efficiency and safety in chemical processes.